CALIFORNIA
FISH-GAME
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u
D
V
VOLUME 72
JANUARY 1986
NUMBER 1
Published Quarterly by
STATE OF CALIFORNIA
THE RESOURCES AGENCY
DEPARTMENT OF FISH AND GAME
—IDA—
STATE OF CALIFORNIA
GEORGE DEUKMEJIAN, Governor
THE RESOURCES AGENCY
GORDON VAN VLECK, Secretary for Resources
FISH AND GAME COMMISSION
BRIAN J. KAHN, President
Santa Rosa
ABEL C. GALLETTI. Vice President WILLIAM A. BURKE, Ed.D, Member
Los Angeles Brentwood
ROBERT BRYANT, Member ALBERT C. TAUCHER, Member
Yuba City Long Beach
HAROLD C. CRIBBS
Executive Secretary
DEPARTMENT OF FISH AND GAME
JACK C. PARNELL, Director
1416 9th Street
Sacramento 95814
CALIFORNIA FISH AND GAME
Editorial Staff
Editorial staff for this issue consisted of the following:
Wildlife William E. Grenfell, Jr.
Anadromous Fish Kenneth A. Hashagen, Jr.
Marine Resources Robert N. Lea, Ph.D.
Striped Bass Donald E. Stevens
Editor-in-Chief Perry L. Herrgesell, Ph.D.
CONTENTS
Page
Population Characteristics of Pacific Herring, Clupea harengus
pallasi, in Humboldt Bay, California Douglas J. Rabin
and Roger A. Bamhart 4
The Striped Bass Sport Fishery in the Sacramento-San Joaquin
Estuary, 1969-1979 James R. White 17
Food of Juvenile Chinook, Oncorhynchus tshawytscha,
and Coho, O. kisutch, Salmon off the Northern Oregon
and Southern Washington Coasts, May-September 1980
Robert L. Emmett,
David R. Miller and Theodore H. Blahn 38
Line-Transect Censuses of Fallow and Black-Tailed Deer on
the Point Reyes Peninsula Peter J. P. Gogan,
Steven C. Thompson and Reginald H. Barrett 47
Notes
Utilization by Salt Marsh Harvest Mice,
Reithrodontomys raviventris halicoetes, of a
Non-Pickleweed Marsh Fred Botti,
Dee Warenycia and Dennis Becker 62
A Method for the Efficient Removal of Juvenile Saimonid
Otoliths Brian D. Winter 63
4 CALIFORNIA FISH AND GAME
Calif. Fish and Came 72(1 ): 4-16 1986
POPULATION CHARACTERISTICS OF PACIFIC HERRING,
CLUPEA HARENGUS PALLASl, IN HUMBOLDT BAY,
CALIFORNIA 1
DOUGLAS J. RABIN 2 AND ROGER A. BARNHART
California Cooperative Fishery Research Unit
Humboldt State University
Areata, California 95521
Population characteristics of Pacific herring, Clupea harengus pallasi, were
determined for spawning stocks in Humboldt Bay. Fecundity was estimated to be
220 ±35 eggs per gram. Biomass of hearring was estimated to be 372 tons (237mt)
in 1974-75 and 232 tons (210mt) in 1975-76. Spawning occurred from early December
to early March both years, primarily in north Humboldt Bay. Two- and three-year-old
herring accounted for about 46% and 57% by number respectively for the 1974-75
and 75-76 spawning stocks.
INTRODUCTION
In 1972, Japan removed its import quota on herring roe which stimulated the
market for herring and encouraged development of herring fisheries from
California to Alaska. The present study was designed to obtain information
needed for management of the Humboldt Bay herring fishery.
The biology of Pacific herring, Clupea harengus pallasi, has been extensively
studied for more than half a century (Rounsefell 1930, Taylor 1964,
Blankenbeckler 1978, Spratt 1981). Pacific herring spawning grounds extend
from southern California along the North Pacific rim to Japan. Spawning occurs
in inshore waters, bays, and estuaries, beginning in the late fall in California and
lasting up to four months.
When herring schools move into shallow inshore waters, they become highly
vulnerable to commercial fisheries. Fishery managers must know when
spawning occurs and where spawning schools are located to regulate the fishery.
The objectives of the present study were (i) record the time and distribution of
herring spawning in Humboldt Bay for two seasons, (ii) estimate biomass of the
spawning population and of the spawning substrate, and (iii) determine age
structure, maturity, and sex ratio of adult herring in Humboldt Bay. A concurrent
studv determined the fecundity of Humboldt Bay herring (Rabin and Barnhart
1977).
DESCRIPTION OF STUDY AREA
The 22.4 km-long Humboldt Bay is about 144 km south of the
California-Oregon border (Figure 1). It is a marine embayment having small
localizaed habitats with true estuarine characteristics (U.S. Army Corps of
Engineers 1976). Skeesick (1963) presented an extensive description of the
physical and chemical characteristics of Humboldt Bay.
1 Part of a thesis submitted by the senior author to Humboldt State University in partial fulfillment of a Master of
Science degree.
2 Mr. Rabin's present address is: P.O. Box 342, Kirkland, Washington 98033. Accepted for publication March
1985.
POPULATION CHARACTERISTICS OF PACIFIC HERRING
ARCATA
PAC I F I C
OCEAN
MAP LOCATION
FIGURE 1. Map of Humboldt Bay, California
Large beds of eelgrass, Zostera marina, grow from mud flats that characterize
north and south Humboldt Bay (Figures 2 and 3). Harding, Butler, and Heft
(1975) estimated that the north and south bays had 4.35 X 10 6 m 2 and 8.86 X
1 0 6 m 2 of eegrass, respectively. Mud flats and eelgrass beds are exposed at most
minus tides and are divided by a network of narrow channels. Distribution of
eelgrass is limited primarily to shallow mud flat areas due to high water turbidity
and tidal scouring along channel edges. Eelgrass is the primary herring spawning
substrate in Humboldt Bay.
CALIFORNIA FISH AND CAME
PAC I F I C
OCEAN
|.Vv.::-'--| EELGRASS
A- I SPAWNING LOCATIONS
%
ARCATA
%
%i
°"> i
MUD
MUD
METERS
_i
1000
2000
NORTH HUMBOLDT BAY
FIGURE 2. Map of north Humboldt Bay at 0-tide. Stippled areas indicate eelgrass distribution for
winters 1974-75 and 1975-76.
HISTORY OF FISHERY
The Bay has supported a relatively small bait and commercial herring fishery
for over 50 years. A total of about 630 1 of herring were harvested from 1 926-76;
the largest annual catch, 63 t was taken in 1943. There were no commercial
landings of herring in 1965-72. In 1975 and 1976, 1 and 11 t respectively, were
caught under temporary state legislation allowing a winter harvest of 20 t. The
state increased the harvest quota to 50 t in 1977 and the quota was approached
each year from 1979 through 1981 and exceeded in 1982 (Table 1 ). The quota
was increased to 60 t in 1983.
METHODS AND MATERIALS
Fish Sampling
Herring were caught in 1974-75 with a variable mesh sinking nylon gill net,
38.1 by 1.8 m with equal lengths of 1.3, 1.9, 2.5, 3.2 and 3.8 cm bar mesh. The
net was allowed to soak no more than 10 min per set in areas where birds and
POPULATION CHARACTERISTICS OF PACIFIC HERRING
seals were actively feeding. During 1975-76 a 60.9 by 6.1 m beach seine was
used for sampling and a recording fathometer used to locate the fish.
The following data were recorded for each fish sampled; standard length in
mm, weight to the nearest 0.1 g, sex, and maturity. Scales were removed for age
determination. Fish caught in the 1974-75 season were categorized as being
either immature, having undeveloped gonads, or mature, with gonads filling the
body cavity (Bagenal and Braum 1971 ). In the 1975-76 season mature fish were
further categorized as having opaque (ripening) or translucent (ripe) eggs.
PACIFIC OCEAN
SPAWNING LOCATIONS,
EELGRASS
SOUTH HUMBOLDT BAY
METERS
i
2000
FIGURE 3. Map of south Humboldt Bay at 0-tide. Stippled areas indicate eelgrass distribution for
winters 1974-75 and 1975-76.
Scales used for age determination were taken from the area below and anteri-
or to the dorsal fin, then mounted between two glass plates and aged without
reference to fish length. An annulus at the outer edge of the scale was assumed
on scales of herring caught during the spawning season. For example, a herring
hatched in January 1974 and caught in January 1976 was considered a 2-year-
old, although showing only one annulus inside the scale margin.
8 CALIFORNIA FISH AND CAME
TABLE 1. Pacific Herring Landings, Humboldt Bay, California. 1974-1983.
* Landings Quota
Year Tons Pounds (tons)
1974 0.2 500 20
1975 1.0 2,000 20
1976 11.6 23,134 20
1977 21.5 42,949 50
1978 11.7 23,417 50
1979 49.4 98,831 50
1980 49.5 98,981 50
1981 43.0 85,920 50
1982 51.6 103,280 50
1983 9.5 18,980 60
• Ron Warner, California Department of Fish and Came Eureka, Ca. (pers. comm.).
Spawn Surveying
Time, distribution, and density of spawns were determined for the winters of
1974-75 and 1975-76. From late November to late March, daily surveys of
eelgrass beds were conducted, alternating days between north and south Hum-
boldt Bay. Surveying was done from a 5 m flat bottom boat. Two garden rakes,
wired back to back and attached to the boat with a 10 m rope, were used to
uproot eelgrass and examine it for attached eggs. The rake was used to outline
spawning areas with the aid of buoys, duck blinds, and other landmarks as
reference points. We installed 5 m wood poles as additional channel markers
to facilitate surveying at higher tides.
The modified rake was randomly cast from a boat in a spwaning area to obtain
3-16 samples of 100-400 g of eelgrass on which eggs had been deposited in
order to calculate mean number of eggs per kg of eelgrass. The size of the
spawning area and density of egg deposition determined the number of samples
collected. After roots were removed, each sample was placed in a plastic bag,
brought to the laboratory, rinsed clean of sediment, and allowed to drain. Leaves
were weighed to the nearest 0.1 g and preserved in 10% formalin. Eggs in each
sample were hand counted and mean number of eggs per kg of eelgrass was
estimated for each spawning area.
Fish sometimes spawned two or more times in areas that already contained
unhatched eggs. Even though the first spawn had already been measured and
sampled it was difficult to determine the extent of overlap and relative density
of the more recent egg deposition. In such instances water temperature and egg
development were monitored and hatching time for the first spawn was predict-
ed according to Alderdice and Velson (1971 ) and Taylor (1971 ). After the first
eggs hatched, the more recently deposited eggs were measured and sampled as
a single unit. The estimates were calculated and reported as separate spawns.
Mean weight/m2 of eelgrass was obtained by sampling eelgrass during day-
time minus tides in February and March. A 0.15 m2 hoop was cast randomly in
areas where spawning occurred. Eelgrass rooted within the hoop was cut to
exclude the roots and bagged. Samples were brought to the laboratory, rinsed
clean of sediment, drained, and weighed to the nearest 0.1 g. Mean weight/m2
values were derived each winter for areas having light and medium eelgrass
growth, as classified by Harding (1973).
POPULATION CHARACTERISTICS OF PACIFIC HERRING 9
Number of kilograms of eelgrass on which eggs were laid was determined by
multiplying the spawning area in m 2 by mean weight of eelgrass per m2 within
the same area. We used a polar planimeter and Coast and Geodetic Survey chart
of Humboldt Bay to measure the previously outlined spawning area.
Fecundity
The mean number of eggs per gram of fish was derived from a concurrent
fecundity study of Humboldt Bay herring (Rabin and Barnhart 1977). We deter-
mined the mean number of eggs per gram of female herring to be 220 ± 35
(95% CI) for ages 2-9.
Biomass Estimation
Biomass of herring in each spawning school was determined by the following
equation:
B C
D
where:
A = grams of fish spawning
B = kilograms eelgrass on which eggs were deposited
C = mean number of eggs per kilogram of eelgrass
D =mean number of eggs per gram of spawning adults (sexes combined)
Confidence limits of final biomass estimates were calculated from the com-
bined variance for eggs/kg eelgrass of all samples taken for the respective
season.
The sex ratio of adult herring in both years did not differ significantly from 1:1,
therefore, the value (D) used for fish biomass computations was 220/2 or 110
eggs per gram of herring for both sexes.
RESULTS
Age and Growth Relationships
During January and early February 1975, herring were caputured near spawn-
ing areas Ui>ing a variable-mesh gill net. In 1976 a beach seine was used to
capture herring. Adult herring, 2 to 1 1 years old, were found in the spawning
populations in both years. For 1974-75 and 1975-76, respective mean lengths
ranged from 157 to 230 mm and 166 to 223 mm, and mean weights from 63 to
195 g and 79 to 178 g (Table 2). Two-years-olds from the 1975-76 catch were
markedly longer and heavier than 2-year-olds from the 1974-75 catch. Length
overlapped considerably among all adjacent age groups (Figure 4). Two- and
three-year-old herring far outnumbered all other age groups (Figure 5) but were
not distinguishable by length alone (Figure 6).
Ages 2 and 3, combined, accounted for 57.1% by number and 43.8% by
weight offish spawning in 1975-76 (Table 2). No young of the year or yearlings
were taken in either season.
Maturity
Of 408 adult herring examined in 1974-75, 96% were mature. All herring
caught in 1975-76 were mature; most (99%) were in ripe or running ripe
condition.
10
CALIFORNIA FISH AND CAME
TABLE 2. Year Class Statistics for
1974-75 and 1975-76.
Season
and age Year
group class
1974-75
2 1973
3 1972
4 1971
5 1970
6 1969
7 1968
8 1967
9 1966
10 1965
11 1964
1975-76
2 1974
3 1973
4 1972
5 1971
6 1970
7 1969
8 1968
9 1967
10 1966
11 1965
1 From gill net catches.
2 From seine catches.
2^0
230
220
Humboldt Bay, Pacific Herring Caught During Winters
210
200
c
01
\~190
10 «-«
% 180
u
170
160
150
1U0
T
T
T
I
I
T
I 1
1
Mean
Mean
Percent
Percent
standard
weight
mber
number
weight
length (mm)
<g>
75
29.6'
15.3
157
63
42
16.6
14.0
179
103
41
16.2
16.2
190
122
19
7.5
9.4
205
153
11
4.3
6.5
212
181
19
7.5
10.7
212
173
30
11.9
18.0
218
185
11
4.4
7.0
224
195
3
1.2
1.7
217
173
2
0.8
1.2
230
191
97
33.6 2
22.9
166
79
68
23.5
20.9
183
102
33
11.4
12.3
197
123
28
9.7
12.1
204
142
14
4.8
6.8
212
159
10
3.5
5.1
217
168
25
8.7
13.0
219
170
10
3.5
4.9
218
160
3
1.0
1.6
221
178
1
0.3
0.4
223
153
„ T
T
t T
1
H 11
I
1
t
I
1
*
III
11 l 1
I
. 1974-75 winter range and •
" 1975-76 winter range and o
FIGURE 4.
1 2 3 ^ 5 6 7 8 9 10 II
Age ( Yeors)
Age and length relationships for Humboldt Bay herring caught during winters 1974-75
and 1975-76.
POPULATION CHARACTERISTICS OF PACIFIC HERRING
11
kO
30
20
c
V
u
L.
0>
0.
10
l 23^56789 10 11
Age (yr)
FIGURE 5. Age composition of 289 Humboldt Bay herring, January 1976.
}k
c
a>
u
L.
a>
12
10
8
6
1M).5 150.5 160.5 170.5 180.5 190.5 200.5 210.5 220.5 230.5 2U0.5
Standard Length (mm)
FIGURE 6. Length groups for 289 Humboldt Bay herring, January 1976.
1 2 CALIFORNIA FISH AND CAME
Eelgrass Biomass Estimates
Eelgrass biomass estimates for areas where spawning occurred were derived
from 50 samples taken in 1974-75 and 71 samples in 1975-76 (Tables 3, 4).
Eelgrass density was variable from year to year. In 1975-76 eelgrass biomass
in north Humboldt Bay was 25% less than in 1 974-75. However, areas classified
by Harding (1973) as having light eelgrass growth (Figure 2, areas A-D) had
more eelgrass biomass each year than did Harding's areas of medium growth
(Figure 2, areas E-l).
Eelgrass biomass per unit of area is typically higher in south Humboldt Bay
than in north Humboldt Bay (Harding 1973). Spawning biomass estimates for
south Humboldt Bay are conservative because due to time constraints we used
north bay eelgrass density values in our calculations.
Herring Biomass Estimation
Random samples of eggs on eelgrass were collected nine times in 1 974-75 and
eight times in 1975-76. The number of spawns each winter was greater than the
number of sampling dates, judging by the occurrence of intermittent overlapping
spawning. These intermittent spawnings were observed in January and February
of both seasons.
Spawning began in mid-December and ended in early March; about 99%
occurred between December 14 and February 14. More than 99% of the total
egg deposition was in north Humboldt Bay — 80% in the eelgrass beds southeast
of Bracut channel (Figure 2, Area A).
Estimated Humboldt Bay Pacific herring spawning biomass was 372 ±8 t in
1974-75 and 232 ±6 t (95% CI) in 1975-76. In addition 1 t (0.9mt) of adult
herring was taken commercially in 1974-75 and 11 t (10mt) were caught in
1975-76 in Humboldt Bay (Tables 3, 4).
DISCUSSION
Most herring spawning took place in Humboldt Bay during December through
March, the same months in which spawning occurred in San Francisco and
Tomales Bays, California (Spratt 1976, 1981 ). Eighty percent of all spawning in
Humboldt Bay occurred in the North Bay eelgrass beds nearest the creeks
flowing into the bay. South Humboldt Bay receives comparatively little fresh
water and was practically unused by herring — even though South Bay has more
than twice the eelgrass biomass of North Bay. Outram (1951 ) found that low
salinity water stimulated herring to spawn while in captivity. Taylor (1971)
reported that hatching success decreases with increasing salinity. The location
of fresh water inflow apparently influenced the location of herring spawning in
Humboldt Bay.
Seasonal catches of Humboldt Bay herring did not exceed 12 t (10,980 kg)
from 1959 through 1976. From 1979 through 1982 landings approximated 50 t
annually. We believe that the population characteristics during our data collec-
tion period resemble those of an unexploited resource.
Our sampling data show full recruitment of herring into the spawning stock
at age 2. Spratt ( 1 981 ) , from his work on San Francisco and Tomales Bay herring
populations, states that California herring enter the spawning population at 2
years of age and by age 3 all herring are mature. Recruitment of British Columbia
POPULATION CHARACTERISTICS OF PACIFIC HERRING
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POPULATION CHARACTERISTICS OF PACIFIC HERRING 15
herring occurs primarily at ages 3 and 4 (Outram and Hymphreys 1974). The
infrequency of spawning checks or false annuli on the scales we examined
indicated that the herring spawning season in Humboldt Bay does not overlap
significantly with the resumption of growth in late winter and spring.
Since seasonal abundance of eelgrass in north Humboldt Bay can be substan-
tially influenced by water quality (Harding 1973), bird feeding rates (Yocum and
Keller 1961 ), and oyster culture (Waddell 1964), the annual change in eelgrass
density we observed was not unusual. Our eelgrass biomass values represent
only the wet weight of eelgrass leaves since the rhizome is an inaccessible
substrate for herring eggs.
Field observations indicate that herring eggs do not adhere well to eelgrass
coated with sediment or decaying epiphytes. Our herring biomass estimates are
conservative due to the detachment of eggs between sampling periods, which
Hart and Tester (1934) attribute to wave action.
Although bird predation of herring eggs can account for high removal rates
of eggs before hatching (Cleaver and Frannett 1946, Outram 1958, Steinfeld
1972, Spratt 1981 ), we believe that predation was not a significant factor in the
calculation of Humboldt Bay herring biomass estimates. Few to no bird aggrega-
tions were observed at Humboldt Bay spawning sites, regardless of tidal height.
Spawning intensity was relatively light, which according to Spratt (1976) makes
bird predation on eggs difficult.
Our 1974-75 and 1975-76 spawning biomass estimates of 372 t (337mt) and
232 t (210mt) should be useful for management purposes. Humboldt Bay can
sustain a small commercial herring fishery from mid-December through March
each year. North Bay eelgrass beds, the primary spawning locale of Humboldt
Bay herring, should be given maximum protection to insure adequate herring
reproduction in the bay.
ACKNOWLEDGMENTS
This work was performed as part of NOAA Sea Grant Contract 04-5-158-28,
"Studies on the biology of Northern Anchovy and Pacific Herring in Humboldt
Bay" under the direction of the California Cooperative Fishery Research Unit,
U.S. Fish and Wildlife Service. We appreciate the efforts of K. Bates, D. Chess-
more, M. Dresner, S. Eisele, E. Spurling and associated personnel of the Califor-
nia Cooperative Fishery Research Unit. Our thanks to the California Department
of Fish and Game which provided some matching funds for the project and
especially biologist J. Spratt who provided considerable guidance in the early
phases of our research.
LITERATURE CITED
Alderdice, P.F. and F.P.J. Velson. 1971. Some effects of salinity and temperature on early development of Pacific
herring, Clupea pallasi. Can. Fish. Res. Board, Jog., 28:1545-1562.
Bagenal, T.B., and E. Braum. 1971. Eggs and early life history. Pages 166-198 in W.E. Ricker, ed. Methods for
assessment of fish production in fresh waters. 2nd ed. Blackwell Scientific Publications, Oxford.
Blankenbeckler, D. 1978. Age, growth, maturation and parasite occurrence of Pacific herring Clupea pallasii from
southeastern Alaska, 1974 through 1976. Alaska Dept. Fish Game Tech. Data Rep. No. 39. 88 p.
Cleaver, F.C, and DM. Franett. 1946. The predation by seabirds upon the eggs of Pacific herring, Clupea pallasii,
at Holms Harbor during 1945. State of Washington, Dep. Fish., Div. Sci. Res., Biol. Rep. 46 B, 18 p.
Harding, L.W. )r. 1973. Primary production in Humboldt Bay. Thesis, Humboldt State College, Areata, Ca, 55 p.
Harding, L.W., Jr., J.H. Butler, and R.E. Heft. 1975. The standing stock and production of eelgrass, Zostera marina
L. in Humboldt Bay, California. Lawrence Livermore Lab., Livermore, CA., No. UCRL-76987. 18 p.
16 CALIFORNIA FISH AND GAME
Hart, J.L. and A.L Tester. 1934. Quantitative studies on herring spawning. Trans. Am. Fish. Soc, 64:307-312.
Outram, D.N. 1951. Observations on the retention and spawning of the Pacific herring. Prog. Rep. Biol. Stn.
Nanaimo and Prince Rupert 87:32-33.
1958. The magnitude of herring spawn losses due to bird predation on the west coast of Vancouver
Island. Fish. Res. Board Can. Pac. Prog. Rep., 111:9-13.
Outram, D.N. and R.D. Humphreys. 1974. The Pacific herring in British Columbia waters. Fish. Mar Serv ., Pai
Biol. Stn. Circ, 100, 26 p.
Rabin, D.|. and R.A. Barnhart. 1977. Fecundity of Pacific herring, Clupea harengus pallasi, in Humboldt Bay. Calif.
Fish. Came, 63(3):193-196.
Rounsefell, G.A. 1930. Contribution to the biology of the Pacific herring, Clupea pallasii. and the condition of the
fishery in Alaska. Bull. U.S. Bur. Fish., 45:227-320.
Skeesick, DC. 1963. A study of some physical-chemical characteristics of Humboldt Bay. Thesis, Humboldt State
College, Areata, CA, 148 p.
Spratt, |.D. 1976. The Pacific herring resource of Tomales Bay and San Francisco Bay, California: Its size and
structure. Calif. Fish Game, Mar. Resources Tech. Rep. 33, 44 p.
1981. Status of the Pacific herring, Clupea harengus pallasii, resource in California 1972 to 1980. Dept
of Fish Came, Fish Bull. (171), 107 p.
Steinfeld, J.D. 1972. Distribution of Pacific herring spawn in Yaquina Bay, Oregon, and observation on mortality
through hatching. Thesis, Oregon State Univ., Corvallis, 75 p.
Taylor, F.H.C. 1964. Life history and present status of British Columbia herring stocks. Can. Fish. Res. Board, Bull.,
143, 81 p.
1971. Variation in hatching success in Pacific herring, Clupea pallassil, eggs with water depth, tempera-
ture, salinity and egg mass thickness. Rapp. P.-V. Reun. Cons. Int. Explor. Mer, 160:34-^41.
U.S. Army Corps of Engineers. 1976. Navigation channel improvements authorized for Humboldt Harbor and Bay,
Humboldt County, California. U.S. Army Corps of Engineers Draft Environmental Statement. San Francisco
District, CA. 79 p.
Waddell, J.E. 1964. The effect of oyster culture on eelgrass, Zostera marina, L., Thesis, Humboldt State College,
Areata, CA, 48 p.
Yocum, C.F., and M. Keller. 1961. Correlation of food habits and abundance of waterfowl, Humboldt Bay,
California. Calif. Fish Came, 47:41-53.
THE STRIPED BASS SPORT FISHERY 17
Calif. Fish and Came 72 ( 1) : 1 7-37 1 986
THE STRIPED BASS SPORT FISHERY IN THE
SACRAMENTO-SAN JOAQUIN ESTUARY, 1969-1979 1
JAMES R. WHITE
California Department of Fish and Game
Bay-Delta Fishery Project
4001 N. Wilson Way
Stockton, California 95205
The fishery for striped bass in the Sacramento-San Joaquin Estuary is described
from tag returns and a bay-area creel census. Annual harvest averaged 18% and was
higher for bass > age 5. Annual catch ranged from about 100,000 to 400,000 fish and
declined after 1976. Angler effort and success (catch/ang h) also declined in the late
1970's. The catch varied both seasonally and geographically; 80% of the catch oc-
curred from May through November, mostly in San Francisco Bay. Private boat
anglers took 65% of the catch, shore/pier anglers took 21%, and charter boat anglers
14%. Fork length of bass in the catch averaged 65.1 cm, but exhibited a downward
trend and varied among segments of the fishery. Age 3, 4, and 5 bass comprised
two-thirds of the catch; age 4 typically was the most numerous group. Female bass
were more numerous than males in the bay area catch in 10 of 11 years. Trends and
anomalies in these data are discussed in relation to striped bass population charac-
teristics, environmental factors and methodological bias.
INTRODUCTION
Striped bass, Morone saxatilis, are the object of an extensive sport fishery in
the Sacramento-San Joaquin Estuary. During the period covered by this report
(1969-1979), sportfishing regulations included a three-fish bag limit and a mini-
mum total length (tl) of 40.6 cm. Angling occurs throughout the year, but
activity varies seasonally in accordance with striped bass migrations. In summer
and fall, anglers fish the ocean beaches with bait or by casting lures. Boat anglers
fish San Francisco Bay and the Pacific Ocean (Figure 1 ) by drifting live ancho-
vies or shiner perch or by trolling lures. In San Pablo Bay and Carquinez Strait
there is a summer evening troll fishery and from San Pablo Bay upstream many
anglers still-fish with bait such as staghorn sculpins ("bullheads"), Leptocottus
armatus; yellowfin gobies ("mudsuckers"), Acanthogobius flavimanus; bay
shrimp, Crangon sp.; northern anchovies, Engraulis mordax; sardines, Sardinops
sp.; and threadfin shad, Dorosoma petenense, primarily in fall and winter. During
spring, most fishing is in the Delta and upriver areas where anglers troll artificial
lures or fish with bait.
My report describes this striped bass fishery from 1969 to 1979. Information
is presented on harvest rate; the magnitude, distribution, and length, age and sex
composition of the catch; fishing effort; and catch rates. Changes in these catch
statistics reflect the condition of the fishery and assist in evaluating resource
management decisions.
METHODS
Harvest rates, annual catch, the seasonal and geographic distribution of the
catch, and the contribution of charter boats, private boats and shore or pier were
estimated from tag returns.
1 Accepted for publication April 1985.
18
CALIFORNIA FISH AND CAME
FEATHER
RIVER
FICURE 1. Sacramento-San Joaquin River System and Estuary.
Legal size striped bass ( >40.6 cm tl, about age 3 and older) were tagged
during their spring spawning migration, on the San Joaquin River near Antioch
and on the Sacramento River between Isleton and Fremont Weir, but primarily
near Clarksburg ( Figure 1 ) . Approximately 4,000-1 8,000 bass were tagged annu-
ally, about 12% of these with $2, $5, $10, or $20 reward tags.
Tags recovered from 0 to 365 days after tagging were designated first year
returns. Since tagging occurred for up to 3 months each spring, recovery years
do not coincide with any specific calendar period, but generally run from spring
to spring.
THE STRIPED BASS SPORT FISHERY 19
Tags were recovered mostly from anglers who voluntarily returned them in
the mail, but also during an annual creel census in the San Francisco-San Pablo
Bay area. Tags observed during the creel census were assumed to be completely
reported; but uncensused anglers did not return all tags that they recovered.
Hence, before calculating harvest rates, mail returns were adjusted for nonre-
sponse based on ratios of return rates of tags of different reward denominations.
I estimated harvest rate using the equation:
ID Rm v
u' - mT (r- + — >
where: u, = harvest rate in year t
M, = number of nonreward tags applied at the beginning of
year t
Rc = number of nonreward tags applied at the beginning of
year t and recovered during the creel census that year
Rm = number of nonreward tags applied at the beginning of
year t and returned in the mail during year t
r = estimated response rate during year t (ratio of nonre-
ward:$20 tag return rate, Stevens, et al. 1985)
I estimated total annual catch of striped bass which were legal size in the
spring using the equation:
A A
C = ON
where: L = estimated catch
u = estimated harvest rate
N = estimated abundance of adult bass.
The abundance of adult bass ( Stevens 1 977a, Stevens et al. 1 985 ) was estimat-
ed using the modified Petersen method (Bailey 1951).
Angler success (bass/angler h) and the length, age, and sex composition of
the summer and fall catch in the San Francisco-San Pablo Bay area were deter-
mined from the creel census. This census was conducted daily from Wednesday
through Sunday at four to 12 ports. It sampled anglers fishing from lower Suisun
Bay to the Pacific Ocean (Figure 1 ).
Census effort was about the same each year except 1977 and 1978 when
private boats were not sampled and charter boat sampling was reduced by
75-80%.
Standard statistical tests (Sokal and Rohlf 1969) were used to evaluate signifi-
cant trends and differences in the various catch statistics. Arcsin transformations
were used before applying these tests to percentages.
RESULTS
Angler Response and Harvest Rate
Angler response, the estimated fraction of recovered nonreward tags that
anglers actually return, decreased over the years of study. Response estimatation
assumed all recovered $20 tags were returned. However, because $20 tags were
not released every year, linear regressions were calculated to describe decreases
in tag return rate ratios of nonreward:$5, $5:$10 and $10:$20 tags, and the three
20
CALIFORNIA FISH AND GAME
return rate ratios predicted annually from these regressions were multiplied to
estimate response for each year (Stevens et al. 1985). Response ranged from
0.58 in 1969 to 0.36 in 1979 (Table 1).
TABLE 1. Summary of Striped Bass Tagging Program in the Sacramento-San Joaquin Estuary.
Bass
Total 1st observed
Bass year tag Response in creel
Ye.tr tagged returns ' rate census
1969 16,419 2,787 0.576 18,458
1970 14,380 1,625 0.551 21,043
1971 18,182 2,860 0.528 18,399
1972 18,368 2,690 0.504 32,381
1973 15,383 2,131 0.481 25,715
1974 13,785 2,616 0.460 38,703
1975 8,853 1,801 0.439 26,993
1976 10,510 1,854 0.419 21,481
1977 2 4,955 860 0.398 4,073
1976 2 4,255 416 0.379 1,461
1979 11,072 1,478 0.360 7,437
Tags recovered within 3(>5 days ot tagging date; includes mail returns of nonreward tags corrected for nonre-
xponse, mail returns of reward tags, and tags recovered during the creel census.
2 Tagging effort reduced from two gill net boats and fyke traps to one gill net boat; private boats not sampled,
charter boat census effort reduced by 75-80%.
From 1969 to 1979, an average of about 18% of the legal-size bass population
was harvested annually (Table 2). Estimated harvest rate declined substantially
from 20% in 1969 to about 13% in 1970 and then increased each year through
1974 when it reached 22%. It remained at that level from 1974 to 1976. The
harvest rate declined in 1977 and again in 1978 to 11%, the lowest level for the
11 -year period. It increased again to almost 18% in 1979, very close to the
11 -year average.
TABLE 1. Estimated Harvest Rate, Legal-Size Abundance and Annual Catch of Striped Bass
in the Sacramento-San Joaquin Estuary, 1969-1979.
Estimated Estimated Estimated
harvest legal-size annual
rate bass abundance catch
)ear (0) (hi) (6= u\)
1969 0.201 1,646,000 330,800
1970 0.133 1,727,000 229,700
1971 0.158 1,600,000 252,800
1972 0.170 1,883,000 320,100
1973 0.174 1,637,000 284,800
1974 0.222 1,477,000 327,900
1975 0.218 1,850,000 403,300
'976 0.229 1,563,000 357,900
1977 0.183 885,000 162,000
'978 0.106 1,009,000 107,000
' 9 0.178 1,125,000 200,300
Mean 0.179 270,600
Standard Deviation 0.0379 89,600
Harvest rate trends were about the same for both sexes. Sex stratified rates
were calculated for ages 3 and 4 combined and ages > 5. Except for females in
1978, bass age 5 and above were harvested at consistently higher rates than 3
and 4-year-olds (Figure 2).
THE STRIPED BASS SPORT FISHERY
03 -i
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FIGURE 1. Harvest rate estimates stratified by age and sex for striped bass in the Sacramento-San
Joaquin Estuary.
Annual Catch
From 1969 to 1979, annual catch estimates ranged from about 107,000 to
403,000 striped bass (Table 2). Catch fluctuated with no significant trend (t =
0.30, P >0.90) from 1969 to 1976; however, it declined substantially in 1977 and
remained low through 1979. The 1977-1979 average of 156,400 bass was signifi-
cantly less than the 1969-1976 mean catch of 313,400 (t = 4.28, P < 0.005).
Seasonal and Geographic Distribution
The harvest of tagged bass was stratified according to recovery month and
area to approximate the seasonal and geographic distribution of the catch. These
distributions are approximations for several reasons: (i) immature female bass
(ages 3 and 4) are underrepresented in the tagged group because many do not
migrate to the spawning grounds where tagging occurs; ( ii ) recruitment of newly
legal (40.6 cm) untagged fish occurs after tagging; and (iii) due to mortality,
tagged fish become less available with time after tagging. The latter two factors
cause tag returns to increasingly underrepresent the monthly catch as time
passes which, in turn, affects the apparent geographic distribution of the catch
because peak fishing periods differ among areas.
Monthly tag returns were low in winter, increased during spring, leveled off
during summer, and reached a peak in the fall before declining to winter levels
(Figure 3). More than 80% of the annual returns were from bass caught from
May through November. Recoveries were highest in October and November.
22
CALIFORNIA FISH AND CAME
0.20-,
O a 0.15
D
z t-
O uj 010
<
UJ
T
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I
F
i
M
i
A
i i i
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i
A
i
S
i
0
1
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D
FIGURE 3. Monthly distribution of striped bass harvest in the Sacramento-San Joaquin Estuary
based on mean first year returns of nonreward tags from 1969 to 1979. Mail returns
were corrected for response rate. Vertical bars represent ± 2 standard errors.
In general, San Francisco Bay provided more tag recoveries than other re-
gions. From 1969 to 1979, these recoveries averaged 35% of the annual total,
but the proportion was highly variable, ranging from about 20% in 1979 to 54%
in 1974 (Table 3).
San Pablo Bay-Carquinez Strait returns averaged about 21% of the total.
Suisun Bay averaged 6.1% and the Delta averaged 19.8% of the total annual
returns. The percentage of tag returns from the Delta exceeded the 11 -year
average each year from 1976 to 1979 resulting in a statistically significant (t =
3.17, P <0.01 ) increasing trend. The percentage of returns from Suisun Bay also
was relatively high during the last 4 years, particularly in 1978 and 1979, but the
11 -year trend was not statistically significant because returns were lower from
1973-1975 than in earlier years.
About 15% of annual tag returns were from the Sacramento River upstream
from the Delta. On the average, returns were equally divided between the
section from Courtland to the Feather River (including the American River) and
the section upstream from there including the Feather River and its tributaries.
The fewest tag recoveries came from the San Joaquin River and the Pacific
Ocean. Only about 1% or less of annual returns were from the upper San
Joaquin River. An average of 2.3% of annual returns were from the Pacific
Ocean, although in 1977 an exceptional 8.4% came from the ocean. Although
bass migrate to the ocean every year, they become available to anglers only
when they congregate near shore, particularly off beaches south of the Golden
Gate.
Fishing Mode
Anglers returning tags were asked if they caught their fish on a charter boat,
private boat, or from shore or pier. This allowed the annual catch to be appor-
tioned accordingly using all returns, including tags applied in previous years.
THE STRIPED BASS SPORT FISHERY
23
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24
CALIFORNIA FISH AND CAME
On the average, private boat, shore, and charter boat anglers accounted for
about 65%, 21%, and 14% of the annual catch, respectively (Figure 4). There
was a statistically significant (t = 4.45, P < 0.005) upward trend in shore anglers'
share of the catch from 1969 to 1979. The fraction of the catch taken on charter
boats and private boats did not significantly increase or decrease over the years
(t = 0.06, P >0.90 and t = 2.22, P >0.05, respectively).
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YEAR
FIGURE 4.
Proportion of annual catch of striped bass in the Sacramento-San Joaquin Estuary taken
from private boats, charter boats, and shore or pier. Calculated using all tags returned,
including first year returns of nonreward tags (creel and response-corrected mail
returns), reward tags, and tags applied in previous years.
Length, Age, and Sex Composition of Catch
The mean fork length (fl) of bass measured in the creel census from 1969 to
1979 was 65.1 cm and ranged from 57.8 cm in 1979 to 72.0 cm in 1977 (Table
4).
Mean length varied with fishing location. Bass caught in the Pacific Ocean
averaged 80.0 cm fl and were consistently larger than those from other areas
( Figure 5 ) . On the average, bass caught in Carquinez Strait and Suisun Bay were
the smallest (51.5 cm). Fish from San Francisco Bay and San Pablo Bay were
intermediate in length, averaging 64.6 cm and 65.4 cm, respectively.
Fish length decreased significantly from 1969 to 1979 in all areas (Pacific
Ocean; t = 3.27, P < 0.01; San Francisco Bay: t = 2.51, P < 0.05; San Pablo
Bay: t = 5.43, P < 0.001; Carquinez Strait-Suisun Bay: t = 2.43, P < 0.05).
THE STRIPED BASS SPORT FISHERY
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CALIFORNIA FISH AND CAME
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FIGURE 5. Annual mean fork length of striped bass caught in four areas of the western Sacra-
mento-San Joaquin Estuary.
Anglers on private boats consistently caught larger fish than anglers on charter
boats (t = 2.62, P < 0.05; Table 4). The overall difference was due to a consist-
ent difference in San Pablo Bay and Carquinez Strait-Suisun Bay (Figure 6). In
the Pacific Ocean, bass caught on private boats and charter boats were of similar
size in most years; in San Francisco Bay, bass caught on private boats were larger
through 1975 and smaller thereafter.
The average bass caught from shore appeared to be intermediate in size
between those caught on the two types of boats, although samples of shore
caught fish were small and lengths were rather variable (Table 4).
From 1969 to 1979, almost two-thirds of the censused catch was comprised
of 3, 4, and 5 year old bass (Figure 7). Overall, 4-year-old fish were the most
abundant age group in the catch and each successively older age group became
less abundant. Two-year-old bass accounted for less than 1% of the catch.
Within individual years, the age composition often deviated from the average
pattern (Figure 7). Age 3 bass were well underrepresented in 1969 (11%), 1973
(10%), and 1977 ( <8%) compared to the 11 year average of about 21%.
Hence, other age classes were relatively more numerous in these years. In 1969,
age 7 and older bass formed 39% of the catch ( 1 1 year average: 22% ) . The 1 973
catch had a high proportion of ages 4-6 (68% compared to the 56% average).
In 1977, 5-8 year old bass accounted for 71% of the catch (average of 46%).
THE STRIPED BASS SPORT FISHERY
27
Conversely, the age composition in 1979 was unusual as 3 year old bass from
the 1976 year class made up almost half the catch, the result of good trolling
during summer evenings in Carquinez Strait. The percentage of old (age >8)
fish declined noticeably during the early 1 970's and remained low except in 1 977
when fishing was good in the ocean.
PACIFIC OCEAN
80-
E
o
Z
O
z
111
-J
o
FIGURE 6.
t 1 1 1 1 1 r
70 72 74 76
YEAR
Annual mean fork length of striped bass caught by charter boat (•) and private boat
( ▲ ) anglers in four areas of the western Sacramento-San Joaquin Estuary. Private boat
catch not sampled in 1977 and 1978.
28
("AMFORNIA FISH AMD GAME
00
e> -
E
n
- -i
JD
"? r
O)
00
to
T
X
- -5
I a
Ui It
a « 5
< 2 -
IT)
J =
n ^-
NOUISOdWOO 30V J.N30«3d
THE STRIPED BASS SPORT FISHERY
29
Significantly moro female than male striped bass were observed in the catch
every year except in 1979 when more males were seen (Table 5). Percent
females averaged 55.5% and ranged from 63.5% of the catch in 1977 to 48.3%
in 1979. For the years during which both charter boat and private boat catches
were censused, percent females in the private boat catch (55.4%) was signifi-
cantly greater than in the charter boat catch (53.1%) ft = 0.93, P < 0.001 ).
TABLE 5. Percent Female Striped Bass in the San Francisco Bav Area Catch, with Result*, of
Chi-Square Tests of the Hypothesis for all Fishing Methods that Number Males —
Number Females.
Year
1969
1970
1971
I972
1971
1974
1975
1976
1977 '
1978'
1979
Mean
Standard Deviation
%
Female
58.6
55.8
56.7
51.5
55.1
51.5
54.9
54.5
63.5
59.6
48.3
55 5
4.21
ALL METHODS
Bass
Sexed
9.075
9,121
12.131
21.227
16.879
29,329
24,241
19,249
3,931
1,291
7,004
X2
265.7
123.8
219.8
19.5
227.1
27.7
235.1
153.2
277.4
48.0
8.2
1,045.3
P <
0.001
0001
0.001
0.001
0 001
0.00 1
0001
0.001
0.001
0.001
0.005
0.001
CHARTER
BOA1S
0/
Female
55.9
53.4
56.0
51.1
54.7
49.9
55.3
53.6
163.5)
(596i
47.6
53.1
293
PRIVATE
BOATS
Female
60 2
>7
.3
-> .-
il.9
55.7
54.1
54.3
55.8
51.8
55.4
I 70
1 Charter boat census was reduced and private boat census eliminated in 1l*77 and 1f»78 rhese years omitted from
the mean values for charter boats and private boats.
On a monthly basis, exceptions to domination of the catch by females oc-
curred mostly during June (Table 6) . In 1 979 when males were dominant, there
were significantly more males than females caught in June and August. That vear
females prevailed in only two months, Juty and December, and then differences
were small.
TABLE 6.
Year
1969.
1970.
1971.
1972.
1973.
1974.
1975.
1976.
1977.
1978.
1979.
Results of Chi-Square Tests of the Sex Ratio in the Striped Bass Catch Observed
in the San Francisco Bay Area. F or f Indicates More Females; M or m Indicates
More Males; =, Equal Numbers of Each Sex. Upper Case Letters Denote Statisti-
cally Significant Difference at a = 0.05.
Jun
ful
Aug
Sept
Oct
•Voi
Dec
Total
F
F
F
F
F
c
m
F
F
F
F
F
f
F
F
F
F
F
m
F
F
F
F
F
F
F
F
M
F
c
F
f
F
F
m
F
F
M
F
F
F
F
F
m
F
F
F
f
1
F
f
F
F
f
F
m
r
m
F
F
f
in
i
1
M
f
M
m
m
—
f
V1
No data.
30
CALIFORNIA FISH AND CAME
Fishing Effort and Success
Approximately 1.4 million angler hours were recorded by the creel census
from 1969-1979. Effort covered by our sample interviews ranged from about
54,000 angler hours in 1979 to almost 200,000 angler hours in 1969 and 1974
(Figure 8). Interviewed effort on private boats declined from about 120,000
angler hours in 1969 to about 15,000 angler hours in 1979 and this trend was
statistically significant (t = 4.36, P < 0.05, no data for 1977 and 1978). Charter
boat effort fluctuated irregularly from 1969 to 1979 with no consistent trend
(data from reduced census in 1977 and 1978 excluded). However, as for private
boats, the lowest effort was in 1979 and it was less than half of the peak effort
in 1974, only 5 years earlier. While my data represent an unknown portion of
the total fishing effort, I believe these trends are valid since census effort was
about equal each year.
125 -
</)
^ 100-
0 <o
I"o 75-
(L O
S2 so-
1 25-
0-
— T"
69
- r
71
—| r
73
YEAR
— r-
75
77
~™ r
79
FIGURE 8. Fishing effort by charter boat (•) and private boat (®) striped bass anglers sampled
in the San Francisco Bay area creel census. Private boats were not sampled and charter
boat sampling effort was reduced by 75-80% in 1977 and 1978.
Angler success (bass/angler h) was estimated from the censused effort and
catch. These estimates of success are biased upward slightly because the census
was designed primarily to gather data for estimating striped bass abundance.
Therefore when several boats landed simultaneously, samplers selected the
boats with the largest catches.
Success was highly variable from 1969-1979 (Figure 9). From 0.10 bass/
angler h in 1969-1971, overall success increased substantially, averaging 0.18
bass/angler h from 1972 to 1974. Success declined in 1975 and 1976. Only
charter boats were censused in 1977 and 1978, and their success was high in
1977 (0.27 bass/angler h) and low (0.11 bass/angler h) in 1978. In 1979 overall
success (0.14 bass/angler h) was about the same as in 1976 and nearly equal
to the 1 969-1 976 average.
THE STRIPED BASS SPORT FISHERY
31
* 0.3 -
O
X
DC
UJ
-I 0.2 -|
O
z
<
8! o.i
O
<
O
\ /.
69
71
- 1 r~
73
YEAR
75
~T~
77
79
FIGURE 9. Striped bass angler success on charter boats (•) and private boats (a) and both
combined ( O ) in the San Francisco Bay Area. Private boats were not sampled in 1977
and 1978.
Mean charter boat angler success (0.20 bass/angler h) was twice that of
private boat anglers (0.10 bass/angler h). Annual variation in success also was
greater for charter boats than for private boats ( F = 8.84, P < 0.01 ) . Charter
boat success ranged from 0.11 (1969, 1978) to 0.28 (1972) bass/angler h com-
pared to a range of 0.08 (1969, 1979) to 0.17 (1974) bass/angler h for private
boats. Based on the 9 years for which comparative data were obtained, the
difference between the success of charter boat and private boat anglers was
statistically significant (t = 4.62, P < 0.001 ). Despite these differences, charter
boat and private boat success were significantly correlated ( r = 0.83, P < 0.01 ) .
After analysis of variance revealed that angler success differed significantly
among areas (charter boats: F = 8.65, P < 0.001; private boats: F = 17.16, P <
0.001 ), an a posteriori stepwise range test (Student-Newman-Keuls test, Sokal
and Rohlf 1969) was used to determine that charter boat anglers were signifi-
cantly more successful (P < 0.01) in San Francisco Bay than in the Pacific
Ocean, San Pablo Bay, or Carquinez Strait-Suisun Bay (Table 7). For private
boats, angler success was similar in the ocean, San Francisco Bay, and Carquinez
Strait-Suisun Bay, but in San Pablo Bay success was significantly lower (P <
0.05).
Except for 1977, when fishing was exceptionally good in the ocean, summer
success was similar in all years. Overall success varied annually primarily due
to differences in fall fishing (Figure 10).
DISCUSSION
My results show declines in the annual striped bass catch and angling effort,
in regions creel censused, during the mid- to late-1970's. However, a more
general decline in the fishery actually has occurred since 1958 (Stevens et al.
32
CALIFORNIA FISH AND GAME
1985). It is attributable to a decline in bass abundance which apparently is due
to: (i) reduced recruitment explained by a decline in the abundance of young
bass and (ii) increased mortality of adults resulting from the increased harvest
rates in the mid-1 970's.
TABLE 7. Mean Angler Success (Bass/Angler h) of Charter Boat and Private Boat Anglers
in the San Francisco Bay Area Striped Bass Fishery. Private Boat Anglers Were Not
Sampled in 1977 and 1978.
CHARTER BOAT
Pacific
Year Ocean
1969 0.096
1970 0.087
1971 0.059
1972 0.213
1973 0.150
1974 0.100
1975 0.183
1976 0.215
1977 0.381
1978 0.097
1979 0.097
69-76, 79 Mean 0.133
Standard Deviation 0.0587
69-79 Mean 0.153
Standard Deviation 0.0927
PRIVATE BOAT
Pacific
Year Ocean
1969 0.178
1970 0.127
1971 0.153
1972 0.145
1973 0.178
1974 0.030
1975 0.033
1976 0.070
1977
1978
1979 0.032
69-76, 79 Mean 0.110
Standard Deviation 0.0623
FISHING AREAS
San
San
Carquinez
Francisco
Pablo
Strait
Bay
Bay
Suisun Bay
0.141
0.051
0.052
0.219
0.071
0.053
0.234
0.051
0.156
0.361
0.098
0.162
0.315
0.066
0.113
0.305
0.089
0.157
0.241
0.124
0.071
0.173
0.126
0.225
0.179
0.118
0.153
0.100
0.123
0.040
0.165
0.107
0.237
0.239
0.087
0.136
0.0749
0.0289
0.0692
0.221
0.093
0.129
0.0802
0.0292
0.0688
San
San
Carquinez
Francisco
Pablo
Strait
Bay
Bay
Suisun Bay
0.137
0.048
0.101
0.171
0.056
0.208
0.154
0.044
0.161
0.168
0.068
0.176
0.154
0.053
0.108
0.190
0.072
0.105
0.131
0.070
0.190
0.091
0.101
0.169
0.086
0.045
0.086
0.142
0.062
0.144
0.0353
0.0182
0.0443
The decline in striped bass abundance indicates that mortality is exceeding
recruitment (Stevens et al. 1985); yet harvest rates, a major component of total
mortality, for 1 969-1 979 are within the range of estimates reported by Chadwick
(1968) and Miller (1974) for 1958-1971. Also, peak harvest rates of about 27%
in the mid-1 970's are lower than exploitation of Atlantic coast stocks (Kohlen-
stein 1981 ) which are fished both for sport and commercially.
I examined the possibility that our harvest rates were underestimated due to
anglers not returning reward tags. To do this, I re-estimated the harvest rates by
(i) extrapolating charter boat catches reported on logs [Stevens 19776 and
THE STRIPED BASS SPORT FISHERY
33
unpublished; adjusted for inaccuracies and nonreporting (Grant 1977)] to total
catch based on the percent of annual catch by charter boats (Figure 4), and (ii)
dividing these total catch estimates by the Petersen population estimates (Table
2). These harvest rate estimates are independent of angler response, but aver-
aged 45% lower than the estimates based on tag returns. Thus, these results did
not provide evidence that the initial harvest rates were underestimated. The
lower re-estimated harvest rates probably are due to error in the charter boat
catch adjustments (Grant 1977) and/or the Petersen estimates of abundance
(Stevens 1977a, Stevens et al. 1985).
My annual catch estimates (Table 2) are minimum estimates because striped
bass abundance estimates used in the calculation pertain to the number of legal
size fish in the spring when only about half of the 3 year old bass are legal size.
The remaining 3-year-olds are recruited during the summer but are not included
in the catch estimate.
Catches are influenced by the amount of striped bass fishing effort — declining
catches are accentuated by the tendency for anglers to fish less when fishing is
poor. For example, the amount of angler effort on charter boats is directly related
to angler success (Miller 1974). While my creel census data does not reveal a
0.4 n
0.3-
0.2
cc
O
X
cc
-I
o
< 0.1
CC
Hi
Q.
S o.
5 0.2
077
CHARTER BOATS
(72-75)
77
0.1-
PRIVATE BOATS
(72-75)
71,76,79)
JUNE
AUG
OCT
— r
DEC
MONTH
FIGURE 10. Monthly striped bass fishing success in years when success was high (1972-1979) (•)
and in years when success was lower (1969-1971, 1976, 1979) (A) for charter boats
and private boats in the San Francisco Bay area. Charter boat success in 1 977 and 1 978
is plotted separately; private boats were not sampled in 1977 and 1978.
34 CALIFORNIA FISH AND CAME
statistically significant correlation between effort and success, it does provide
evidence that effort was reduced by low success. After a disastrous season in
1978, many charter boats in San Francisco Bay responded to declining angler
interest by shifting a major portion of their effort from striped bass to California
halibut, Paralichthys californicus, and rockfish (Sebastes sp.). This "potluck"
strategy contributed to San Francisco Bay providing its lowest percentage of the
total annual striped bass catch in 1979 (Table 3).
The seasonality of the striped bass catch is influenced by their migrations and
feeding activity. Catches increase in the spring when bass occur in high densities
on the spawning grounds and thus attract anglers. However, their vulnerability
does not peak then because their feeding is diminished (Stevens 1966). The
greatest catches generally occur during the summer and fall in San Francisco and
San Pablo bays when the bass feed more actively. Catches are lowest during
winter because fishing effort is reduced by inclement weather, the bass are
widely scattered (Chadwick 1967, Orsi 1971), the water is turbid, and fish
metabolism is low due to low water temperature.
Catches differ geographically each year, apparently due to changes in migra-
tions and environmental conditions. For example, a drought in 1976-1977 re-
duced freshwater flows resulting in increased salinity intrusion and high water
transparency in the Delta and Suisun Bay in fall and winter. Similar conditions
existed in fall-winter, 1978 and fall, 1979 as significant precipitation did not occur
until late in those seasons. Tag returns from both areas increased beginning in
1976 (Table 3). Salinity intrusion may have induced more bass to migrate from
San Francisco Bay to Suisun Bay and the Delta in the fall as suggested by a
negative, although not statistically significant, correlation (r — —0.42) between
Suisun Bay-Delta returns (percent of annual releases) and returns from San
Francisco Bay. Also, clear water may have enhanced fishing as the tag return
rate is positively correlated with water transparency (Figure 11 ).
The mean length of bass in the population declined during the 1970's (Table
4 ) . Apparently the strong year classes of the late 1 950's ( Stevens 1 9776 ) which
provided good fishing for large bass in the late 1960's and early 1970's were
dying out. Since subsequent year classes were weaker, the abundance of large
bass declined. In the mid 1970's, there probably were several moderate year
classes (Stevens et al. 1985) which were subjected to increasing harvest rates
when recruited. This higher mortality would have further reduced the abun-
dance of large bass in subsequent years. The decline in average size continued
in the late 1970's in spite of consistently low recruitment since 1976 (Stevens et
al. 1985).
Considering the downward trend in mean size, the high harvest of large bass
in the Pacific Ocean in 1977 is anomalous. Apparently they were more vulnera-
ble than usual that year. I found that these catches were not consistent with
Radovich's (1963) hypothesis of warm sea temperatures inducing seaward
migrations and higher ocean catches of striped bass. Some of the lowest ocean
catches occurred in 1974, 1975, and 1978 when summer ocean temperatures at
Hopkins Marine Station, Pacific Grove, CA were similar to 1977 (June-August
mean:14.1-14.3°C). Ocean catches were only average in 1972 and 1976 when
summer ocean temperatures were higher (14.9-15.0°C). Possibly, forage fish
were abundant in the surf zone which concentrated the bass so they were
available to anglers in 1977. However, this explanation cannot be tested with
available data.
THE STRIPED BASS SPORT FISHERY
35
The high ocean harvest in 1977 may have been detrimental. It consisted of
a high proportion of females (63.5%) which contributed to a high overall
harvest (28.3%) of females 5 years and older. These fish account for almost all
striped bass egg production which currently may be inadequate in this popula-
tion (Stevens et al. 1985).
In the San Pablo-Suisun Bay region, private boat anglers caught much larger
bass, on average, than charter boat anglers (Figure 6). This difference reflects
private boats fishing extensively with bait for large bass in fall and winter, but
relatively few of them fishing during summer evenings when charter boats are
trolling for smaller bass.
•79 .77
1.0 n
Q
UJ
UJ
0.8 -
Ocm 0.6
< I
H O
0.4 -
I-
O
<
0.2-
76
69
• 78
• 74
75* «71
•72
70*
•73
T
— I 1 1
40 50
SECCHI DISK DEPTH(cm)
1
60
FIGURE 11. Scatter plot of 1st year tag returns from Suisun Bay and the Delta (mean of Oct., Nov.,
and Dec. returns as a percentage of tags released ) and water transparency. December
tag returns were not used for 1973-1979 because transparency data for December
were incomplete. Correlation coefficient = 0.76 (pZO.01) after arcsin transforma-
tion of decimal fractions.
The age composition of the catch varied annually but was particularly unusual
in 1979. Age 3 bass (1976 year class) comprised an abnormally high 45% of the
bay area catch that year (Figure 7), even though when young, their abundance
was among the lowest of the year classes recruited during the 1969-1979 census
(Stevens et al. 1985). Possible explanations are: (i) High vulnerability for age
3 bass in 1979 — catches were high in the Carquinez Strait evening troll fishery.
These bass may have found abundant forage and remained in the Strait through
the summer. Angler success was high (0.24 bass/angler h) and anglers respond-
36 CALIFORNIA FISH AND GAME
ed by increasing effort, (ii) Low abundance of older bass due to only moderate
recruitment in the early 1970's and high mortality in the mid-1 970's (Stevens et
al. 1985) skewing the 1979 age composition toward the new recruits, (iii) High
survival between ages 0 and 3 for the 1976 year class. These explanations will
be evaluated as appropriate data become available.
More female than male bass were censused every year except 1979. The
system-wide harvest rate is highly variable and there is no consistent pattern
favoring either sex. In the Bay area apparently females are more abundant than
males during the census season. Males dominated the censused catch in 1979
because of the exceptional evening trolling in the summer which exploited small
males returning from spawning.
Angler success during 1969-1979 generally was lower than in 1960 and 1961
(Chadwick and Albrecht 1965) when bass were more abundant (Stevens et al.
1985). Differences between charter boat and private boat success and between
success in San Francisco and San Pablo bays were similar to 1960-1961.
On average, charter boat anglers were twice as successful as private boat
anglers, primarily because charter boat operators are skilled at fishing and know
the productive locations. Average angler success also varies more both seasonal-
ly and annually on charter boats than on private boats. While some private boat
anglers are as skilled as charter boat operators, many are inexperienced and fish
only occasionally, primarily when they hear good reports. Thus, good fishing
results in increased effort on both charter boats and private boats, but average
catch/angler h increases less on private boats causing less variable success
statistics.
ACKNOWLEDGMENTS
Recognition is due to the many Department of Fish and Came employees who
contributed to the striped bass tagging program, the creel census, and the proc-
essing of tag returns through the years. J. Bybee, R. Rogers and J. Grant super-
vised the creel census crews through 1977. I thank B. Collins for suggestions
regarding statistical analyses and D. Stevens, D. Kohlhorst and H. Chadwick for
their critical reviews of this manuscript. K. Odenweller drew the figures. This
work was performed as part of Dingell-Johnson Project F-9-R, "A Study of
Sturgeon, Striped Bass, and Resident Fishes" supported by Federal Aid to Fish
Restoration Funds.
LITERATURE CITED
Bailey, N. J. ). 1951. On estimating the size of mobile populations from recapture data. Biometrika, 38:293-306.
Chadwick, H. K. 1967. Recent migrations of the Sacramento-San Joaquin striped bass population. Am. Fish. Sot.,
Trans., 96(3):327-342.
1968. Mortality rates in the California striped bass population. Calif. Fish Game, 54(4):228-246.
Chadwick, H. K., and A. B. Albrecht. 1965. The summer and fall striped bass fishery during 1960 and 1961. Calif.
Dept. Fish and Came, Inland Fish. Br. Admin. Rept. No. 65-11. 27 pp.
Grant, |. ). 1977. Evaluation of striped bass party boat log reporting for the Sacramento-San Joaquin Estuary from
1969 to 1974. Calif. Fish Game Anad. Fish. Br. Admin. Rept. No. 77-8. 20 pp.
Kohlenstein, L. C. 1 981 . On the proportion of the Chesapeake Bay stock of striped bass that migrates into the coastal
fishery. Am. Fish. Soc, Trans., 110(11:168-179.
Miller, L. W. 1974. Mortality rates for California striped bass (Morone saxatilis) from 1965-1971 . Calif. Fish Game,
60(4)157-171.
Orsi, J. J. 1971. The 1965-1967 migrations of the Sacramento-San Joaquin Estuary striped bass population. Calif
Fish Game, 57(1 ):257-267.
THE STRIPED BASS SPORT FISHERY 37
Radovich, |. 19M. Effect of ocean temperature on the seaward movements of striped bass, Roccus saxatilis, on
the Pacific coast. Calif. Fish Came. 49(3):191-206.
Sokal, R. R , and F I. Rohlf 19f,9. Biometry. W. H Freeman and Co. 776 pp.
Stevonv D. t 1 966 Food h.ibits of striped bass, Roccus saxatilis, in the Sacramento-San Joaquin Delta. Calif. Dept.
Fish and Came. Fish Bull (1*6) 68-96.
Stevens. D. E. 1977,1. Striped bass ( Mnrone saxatilis) monitoring techniques in the Sacramento-San loaquin Estuary.
Pages 91-109. in: W. Van Winkle, ed. Proc. of the Conf on Assessing the Effects of Power-Plant-lnduced
Mortality on Fish Populations. Pergamon Press, Inc., New York.
1 977fc. Striped bass ( Morone saxatilis) year class strength in relation to river flow in the Sacramento-San
loaquin Estuary, California. Am. Fish. Soc, Trans., 106(1 ):34— 42.
Stevens, D. E., D. W. Kohlhorst, L. W. Miller and D. W. Kelley. 1985. The decline of striped bass in the Sacramento-
San loaquin Estuary. Am. Fish. Soc, Trans., 1141 1 ) : 1 2—30.
38 CALIFORNIA FISH AND CAME
Calif. Fish and Came 72(1): 38-^»6 1 986
FOOD OF JUVENILE CHINOOK, ONCORHYNCHUS TSHA-
WYTSCHA, AND COHO, O. KISUTCH, SALMON OFF THE
NORTHERN OREGON AND SOUTHERN WASHINGTON
COASTS, MAY-SEPTEMBER 1980 l
ROBERT L. EMMETT, DAVID R. MILLER, and THEODORE H. BLAHM
Coastal Zone and Estuarine Studies Division
Northwest and Alaska Fisheries Center
National Marine Fisheries Service
National Oceanic and Atmospheric Administration
2725 Montlake Boulevard East
Seattle, Washington 98112
The food of juvenile chinook, Oncorhynchus tshawytscha, and coho, O. kisutch,
salmon captured in the northern Oregon and southern Washington coastal zones
during three cruises, May-September 1980, is described. Fishes were primary prey for
both species during the first cruise. Although diets overlapped, fishes and crab larvae
were primary prey for chinook salmon in the second cruise, while fishes and the
euphausiid Thysanoessa spinifera were important prey for coho salmon. During the
third cruise, hyperiid amphipods were primary prey for both species. There were
relatively few empty stomachs during any cruise. Fullness values are used to discuss
possible food limitations.
INTRODUCTION
Individuals and resource agencies interested in the perpetuation of Pacific
salmon, Oncorhynchus spp., in the Pacific Northwest are becoming more aware
of the need to understand the ecology of salmon in the marine environment.
Fewer adult returns of coho salmon, O. kisutch, even though hatchery produc-
tion has been increasing, has recently stimulated interest in this species habits
(Gunsolus 1978). Biologists have concluded that reduced upwelling off the
Pacific Northwest coast has lowered primary production and thus the carrying
capacity for salmonids (Oregon Department of Fish and Wildlife 1982).
Adequate early marine feeding is apparently a critical factor in determining the
resultant number of adult salmon returns (Healey 1980), and yet there are only
limited data concerning the food of juvenile salmon in marine waters. Previous
food studies of salmonids in coastal waters of Oregon and Washington ( Reimers
1964) and other Pacific areas (Silliman 1941, Merkel 1957, Andrievskaya 1957,
Allen and Aron 1958, Ito 1964, LeBrasseur 1966) have been concerned primarily
with adults. Recently, Healey (1978, 1980) described the food habits of juvenile
chinook, O. tshawytscha, and coho salmon collected in British Columbia marine
waters during spring and summer. Peterson, Brodeur and Pearcy ( 1 983 ) present-
ed food habit data of juvenile chinook and coho salmon captured in coastal
waters of Oregon and southern Washington in June 1979.
This paper provides additional information on the feeding of juvenile salmon
in the coastal waters of northern Oregon and southern Washington during the
spring and summer of 1980.
METHODS
Fishes for this study were collected with a purse seine (495 x 30 m) from 10
' Accepted for publication March 1985.
JUVENILE CHINOOK AND COHO FOOD 39
five-station, east-west transects between Tillamook Bay, Oregon, and Copalis
Head, Washington, ( Figure 1 ) . The net was constructed of 32-mm knotted nylon
web with 30 meshes of 127-mm nylon hung along the bottom above the lead
line. The bunt was made of 18-mm knotted nylon web. Three cruises were
conducted beginning 27 May 1980, 4 July 1980, and 28 August 1980; one day
of sampling time was allotted per transect during each cruise. Descriptions of
the sampling vessel, equipment, water quality measurements, fish processing,
and overall catch, along with distribution, abundance, and growth of juvenile
salmonids during the cruises can be found in Miller, Williams, and Sims ( 1 983 ) .
The first 10 individuals of each species (if available) from each seine set were
taken for stomach analysis. All salmonids having a coded wire tag (CWT),
recognized by the absence of an adipose fin, were also sampled. Fish selected
for feeding analysis were measured (fork length, mm) and their stomachs were
removed and fixed in a 4% formaldehyde solution. In the laboratory, stomachs
were transferred to 70% ethyl alcohol. Approximately 600 stomachs were col-
lected; however, not all the stomachs could be analyzed because of time and
funding constraints. All CWT salmon were examined first and a random subsam-
ple of the remaining fish was selected to provide at least 50 stomachs from each
salmon species from each cruise, except Cruise 2 where all stomachs collected
were examined because so few fish were caught. Twenty-one percent of the fish
analyzed were CWT fish.
Stomach contents were identified to the lowest possible taxa with the aid of
a 10X binocular microscope. Food items were counted, blotted, air dried for 10
min, and weighted to the nearest 0.1 mg.
Stomach content data were presented graphically using a method similar to
that of Pinkas, Oliphant, and I verson ( 1 971 ) , where percent number and percent
weight of prey items are represented on the vertical axis and percent frequency
of occurrence of prey items on the horizontal axis. To evaluate the importance
of each prey item we calculated an Index of Relative Importance (IRI) (Pinkas
et al. 1971):
IRI = F (N+W)
where
IRI = Index of Relative Importance,
F = percent frequency of occurence of a prey item for a fish
species,
N = percent number of a prey for a fish species, and
W = percent weight of a prey item for a fish species.
The relative importance of a particular prey item can be more easily identified
by expressing IRI values as percents. Percent IRI was calculated using the for-
mula
IRI
% IRI, = ^- X 100
IRI ,
where
% IRI j = Percent Index of Relative Importance for prey item i,
IRI i = Index of Relative Importance for prey item i, and
IRI , = total of all Indexes of Relative Importance values for prey
items of predator.
40
CALIFORNIA FISH AND CAME
124° 40'
124° W
• •
WASHINGTON
47° N
46° 40'
46° 20'
45° 40'
FIGURE 1. Transects and stations sampled during offshore purse seining for juvenile salmonids,
May-September 1980.
JUVENILE CHINOOK AND COHO FOOD 41
Diet overlap values were calculated between the two species for each cruise
to determine the potential for competition.
C = 2
s
s
s
2 XiY,
/ 2 X2
+
2 Y2
i = 1
i = 1
i=1
where
C = overlap coefficient,
s = food categories (lowest possible taxa),
X i = % weight contributed by food item i for fish species X
(chinook salmon), and
Y | = % weight contributed by same food item i for fish species Y
(coho salmon).
C ranges from 0 (no diet overlap) to 1 (complete overlap). Values >0.6 are
believed to indicate significant overlap (Zaret and Rand 1971).
An index of fullness was used to identify possible differences in feeding
intensity. Fullness was evaluated by subjectively rating stomachs 1 to 7, with 1
being empty and 7 distended (Terry 1976).
RESULTS
Food
The food of juvenile chinook salmon sampled during the three cruises com-
prised six major prey groups (Figure 2). For chinook salmon captured during
Cruise 1, fishes were the most important prey with crab larvae secondary. In
Cruise 2, fishes were again the most important prey, although crab larvae were
more important than in Cruise 1. During Cruise 3, hyperiid amphipods replaced
fishes as chinook salmon primary prey. For coho salmon captured during Cruise
1 , fishes were the primary prey with crab larvae, calanoid copepods, the gamma-
rid amphipod Atylus tridens, and other invertebrates being secondary ( Figure 2 ) .
In Cruise 2, fishes were still primary prey for juvenile coho salmon, but the
euphausiid Thysanoessa spinifera was also important. In Cruise 3, hyperiid am-
phipods were primary prey for coho salmon, with the pelagic gastropod Limaci-
na sp. secondary.
Besides differences in the IRI values of major prey groups (fish, crab larvae,
etc. ) between cruises, there were also changes in the species composition within
prey groups for both species of salmon ( Figures 3 and 4) . For example, in Cruise
1, sand lance, Ammodytes hexapterus; rockfish, Sebastes spp., unidentified Os-
meridae, and digested fish constituted most of the consumed fish; but in Cruise
2, Sebastes spp. alone constituted most of the consumed fish. In Cruise 3,
northern anchovy, Engraulis mordax, and Pacific herring, Clupea harengus pal-
lasi, were the fish primarily consumed. The species composition of crab larvae
consumed also changed between surveys. In Cruise 1, chinook and coho salmon
fed on Dungeness crab, Cancer magister (megalops); hermit crab, Pagurus spp.
(megalops); and porcelain crab, Porcellanidae (megalops); whereas, in Cruise
2, crab larvae were primarily Oregon cancer crab, Cancer oregonensis (mega-
lops).
42
CALIFORNIA FISH AND CAME
100 r
c
0)
(J
a;
Q.
50
FIGURE 2.
Cruise 1
O
m
Fishes
■ + ■; Crab larvae
Panda/as /ordani
Other
At y I us tndens
KSN Calanoid copepods
Hypernd amphipods
Limacina sp.
Cruise 2
Cruise 3
!><] Thysandessa spimfera
The food of juvenile chinook salmon, Oncorhynchus tshawytscha, and juvenile coho
salmon, O. kisutch, captured by purse seine off northern Oregon and southern Wash-
ington during three cruises in 1980. Food is represented by Percent Index of Relative
Importance (%IRI).
CRUISE i
28 May - 7 June
CRUISE 3
28 August - 9 September
100-1
Percent
number
Percent
weignt
100
n= 52 (3 empty)
100 -,
0 c Y s
m^
00
EE
// w
J£
50 30 25 20 20151Q5
Percent
number
Percent
weight
100
n
= 52
(2 empty)
X^= 236.0 mm
BB
Z
II CC
G
F
JJ KK
1
n
I
\Jr
1
— n
75 50
Percent frequency of occurrence
CRUISE 2
4 July - 14 July
100
Percent
number
Percent
weiytit
100
n= 70 (9 empty)
AA
BB
FF|-|GG
HJVhh
1 1 1 1 — I 1 I ill
35 35 25 25 20 2015.
C Cancer magister (megalops)
F Digested fish
G Clupea harengus pa/lasi
0 Ammodytes hexapterus
P Pagurus spp. (megalops)
S Unidentified Osmeridae
V Cirnpedia (larvae)
W Porcellanidae (megalops)
Y Sebastes spp.
Z Thysandessa spimfera
AA Cancer oregonensis (megalops)
BB Hyperoche medusarurn
CC Limacina spp.
DD Pandalus /ordani
EE Unidentified Pleuioiiectidae
FF Vibilia cultripes
GG Neomysis kadiakensis
HH Spir menus tnaleichthys
1 I Parathemistu pacitica
J J Engraulis mordax
KK Sayitta sp.
J10 5
Percent frequency of occurrence
t k .uRE 3. Food ot juvenile chinook salmon, Oncorhynchus tshdvyytscha, captuied by pur>>e seint-
uti northern Oregon and southern Washington during three cruises in lytH). Food is
represented by numeric and gravimetric composition and by frequency ot occurrence
(n = sample size, X = mean fork length). Prey items less than 3% are ummed.
JUVENILE CHINOOK AND COHO FOOD
43
CRUISE 1
28 May - 7 June
100
Percent
number
Percent
weight
100
COP
n-= 50 (2 empty)
X.= 167.0 mm
nJUu
X
Y
1 — I I in imiimi
50 20 201 5 Yq g
CRUISE 3
28 August - 9 September
100-,
Percent
number
Percent
weight
100
BB
CC
n= 50 (0 empty)
X.* 258.8 mm
G F JJ GG
tzrcf
— i — i — i — i — 1 1 1 1
80 50 50 50 35 201510
Percent frequency of occurrence
100
Percent
number
Percent
weight
100
AA
37 (3 empty)
- 188.4 mm
BB
E3=«J/"
c
F
G
N
O
P
Q
R
S
T
U
V
w
X
Y
z
1 1 1 1 — r— rn
35 30 25 25 2015,\,\
10 3
Percent frequency of occurrence
Cancer magister (megalops)
Digested fish
CRUISE 2 G Clupea harrengus pallasi
4 July — 14 July N Calanoid copepods
Ammodytes hexapterus
Pagurus spp. (megalops)
Pinnixa spp. (megalops)
Atylus tridens
Unidentified Osmeridae
Cancer magister (zoea)
Cancer oregonensis (zoea)
Cirripedia (larvae)
Porcellanidae (megalops)
Porcellanidae (zoea)
Sebastes spp.
Thysanoessa spinifera
AA Cancer oregonensis (megalops)
BB Hyperoche medusarum
CC Limacina spp.
GG Neomysis kadiakensis
I I Parathemisto pacifica
JJ Engraulis mordax
FIGURE 4. Food of juvenile coho salmon, Oncorhynchus kisutch, captured by purse seine off
northern Oregon and southern Washington during three cruises in 1980. Food is repre-
sented by percent numerjc and gravimetric composition and by frequency of occur-
rence (n = sample size, X = mean fork length). Prey items less than 3% are omitted.
Diet Overlap
Diet overlap for the two salmon species was highest in Cruise 1 (C = 0.91 )
and lowest for Cruise 3 (C = 0.71 ); Cruise 2 diet overlap value was 0.90. This
indicated significant diet overlap for all three cruises. During Cruises 1 and 2,
chinook and coho salmon utilized similar fish species for primary prey, whereas
during Cruise 3, chinook salmon consumed proportionally more fish than did
coho salmon, which ate more Limacina sp. (Figure 2).
Fullness
The intensity of feeding in juvenile chinook and coho salmon changed
between cruises (Table 1 ). The lowest percentage of empty stomachs for both
salmon species occurred during Cruise 3; the highest occurred in Cruise 2. The
largest percentage of stomachs that were half full or better (percent index of
fullness values of >4) occurred in Cruise 3 for both chinook and coho salmon.
The lowest percentage of stomachs that were half full or better occurred in
Cruise 2 for chinook salmon and Cruise 1 for coho salmon.
/
2
3
4
5
6
7
> 4
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
5.8
13.5
5.8
19.2
25.0
21.2
13.5
78.9
12.2
5.4
13.5
16.2
8.1
14.9
29.7
68.9
3.8
3.9
5.8
11.5
11.5
19.2
44.2
91.7
3.8
21.2
17.3
21.2
13.5
9.6
13.5
57.8
7.9
7.8
2.6
7.9
5.3
28.9
39.5
81.5
0.0
6.0
2.0
18.0
12.0
24.0
38.0
92.0
44 CALIFORNIA FISH AND CAME
TABLE 1. Fullness of Juvenile Chinook, Oncorhynchus tshawytscha, and Coho, O. kisutch,
Salmon Captured by Purse Seine During Three Cruises Off the Coasts of Northern
Oregon and Southern Washington in Spring and Summer 1980. Fish Taken Were
Divided into Categories of Fullness Ranging from 1 (Stomach Empty) to 7
(Stomach Fully Distended).
Species Index of fullness values
Cruise no. and date
Chinook salmon
1 (28 May-7June)
2 (4-15 July)
3 (28 August-9 September
Coho salmon
1 (28 May-7)une)
2 (4-15 July)
3 (28 August-9 September)
DISCUSSION
Our data indicate that the food of juvenile chinook and coho salmon changes
from spring to late summer off the northern Oregon and southern Washington
coasts. This change is probably directly related to changes in prey availability
and abundance. The importance of juvenile nonsalmonid fishes to juvenile
chinook and coho salmon diets in the spring correlates closely with abundance
of coastal fish larvae populations off Yaquina Bay, Oregon, from February
through July (Richardson and Pearcy 1977). The importance of hyperiid amphi-
pods in juvenile chinook and coho salmon diets in late summer is probably
related to their relative abundance at this time. Lorz and Pearcy (1975) found
that the hyperiid amphipod species commonly consumed in this study were
most abundant in plankton off Newport, Oregon, in late summer and fall. There
is evidence that many hyperiid amphipods species have parasitoid relationships
to jellyfish and other gelatinous plankton (Laval 1980). Therefore, jellyfish popu-
lation dynamics may be an important component of juvenile salmonid feeding
at certain times.
Previous studies of juvenile chinook and coho salmon marine feeding indicate
simliar foods. Peterson et al. (1983) found fishes and invertebrates to be impor-
tant prey in juvenile chinook and coho salmon collected off Oregon and south-
ern Washington in June 1979, with euphausiids, amphipods, and crab larvae
numerically important and fishes gravimetrically important. Their data most
closely resemble our data from Cruise 2. Healey (1980) observed that fish
(mainly Pacific herring) were an important prey of juvenile chinook and coho
salmon in the Strait of Georgia, British Columbia. Our data indicate that herring
were important only in late summer. The difference in herring consumption is
probably a result of availability. Our observations, as did those of Healey (1980)
and Peterson et al. (1983), showed that juvenile salmon fed on different prey
in different geographic areas. For example, in Cruise 3, chinook and coho salmon
captured north of the Columbia River consumed many anchovies; whereas,
south of the Columbia River herring were an important prey and anchovies were
rarely found in the diet. These diet differences may be due to patchy distributions
of prey and to relative prey abundances. There also appeared to be a possible
seasonal component to prey patchiness and/or relative abundance. For exam-
ple, during Cruise 3, four prey items occurred in at least 50% of the coho salmon
JUVENILE CHINOOK AND COHO FOOD 45
stomachs, but in Cruise 2, no item had a frequency of occurrence over 50%;
in Cruise 1 only one item had a frequency of occurrence over 50%.
It is difficult to assess the time of poorest feeding, although data from Cruise
2 indicate a possible reduction in feeding. The largest percentage of empty
stomachs for both species occurred during Cruise 2, and this was also when
chinook salmon had the fewest stomachs that were at least half full. Also, in
Cruise 2 the fewest juvenile salmonids were captured (Miller et al. 1983). High
ocean temperature (surface water temperatures for Cruise 2 averaged 15.2°C)
may have caused juvenile salmon to move into deeper water where they could
not be captured by purse seine. Godfrey (1968) found poor juvenile salmonid
captures at high ocean temperatures off British Columbia. Salmonids may also
have migrated to better feeding areas; Healey (1980) found a direct correlation
between coho salmon abundance and amounts of food in their stomachs.
Juvenile chinook and coho salmon showed a large degree of diet overlap for
all three cruises. High diet overlap values may indicate abundant food supply
and not competition (Zaret and Rand 1971 ). The high diet overlap along with
the low percentage of empty stomachs and relatively high percentage of sto-
machs that were greater than half full are evidence that no food shortages
occurred for juvenile chinook and coho salmon off the northern Oregon and
southern Washington coasts in 1980. Growth rates derived from fishes caught
in this study also do not suggest food limitations (Miller et al. 1983).
An important component of the feeding habits of many fish species is the time
of day. Fish used in this study were collected at various times during daylight
hours, yet many salmonid species have diel feeding behavior (Godin 1981).
Prey species also have diel behavior patterns (Alton and Blackburn 1972, Young-
bluth 1976) which may affect salmon feeding rates. Peterson et al. (1983) found
no significant differences in the diets of salmon collected at different times of
the day; however, their information was collected during 1 month in 1979, and
they combined data from many different sampling stations.
To accurately assess potential limitations of salmonid prey in coastal waters
will require a more rigorous study. Salmonid digestion rates, migration patterns,
and feeding behavior, along with prey availability, prey distributions, predation
rates, and prey population dynamics would be required. Of special need would
be a sustained series of offshore collections of juvenile salmon, their prey, and
other biological and physical data during both weak and strong upwelling years.
These data could then be compared to assess the relationship of upwelling to
salmonid feeding.
ACKNOWLEDGMENTS
We thank G. McCabe, J. Monan, and D. Damkaer for their review and advice
on the paper. Particular thanks go to the crew of the FLAMINGO, who per-
formed the ocean purse seining.
LITERATURE CITED
Allen, C. H., and W. Aron. 1958. Food of salmonid fishes of the western north Pacific Ocean. U.S. Fish Wildl. Serv.,
Special Sci. Rept. 237:1-11.
Alton, M. S., and C J. Blackburn. 1972. Diel changes in the vertical distribution of the euphausiids, Thysanoessa
spinifera Holmes, and Euphausia pacifica Hansen, in coastal waters of Washington. Calif. Fish Came,
58(3):179-190.
Andrievskaya, L. D. 1957. The food of Pacific salmon in the northwestern Pacific Ocean (In Russian). Materially
po Biologii Morsxovo Perioda Zhizni Dalnevostochnykh Lososei. p. 69-75. Moscow. (Fish Res. Board Can.
Transl. Ser. 182).
46 CALIFORNIA FISH AND CAME
Godfrey, H . 1 968. Some observations of juvenile marine chum, chinook and coho salmon taken in waters adjacent
to Georgia Strait in 1965. Fish. Res. Board Can. MS Rept. 955:1-19.
Godin, J. G. J. 1981 . Daily patterns of feeding behavior, daily rations, and diets of juvenile pink salmon (Oncorhyn-
chus gorbuscha) in two marine bays of British Columbia. Can. ). Fish. Aquat. Sci., 38:10-15.
Gunsolus, R. T. 1978. The status of Oregon coho and recommendations for managing the production, harvest, and
escapement of wild and hatchery reared stocks. Oreg. Dep. Fish Wildl., Columbia Region, Portland, Oreg.,
59 p.
Healey, M. C. 1978. The distribution, abundance, and feeding habits of juvenile Pacific salmon in Georgia Strait,
British Columbia. Fish. Mar. Serv. Tech. Rep. 788:1^*9.
1980. The ecology of juvenile salmon in Georgia Strait, British Columbia. Pages 203-229 in, W. J. McNeil
and D. C. Himsworth, eds., Salmonid ecosystems of the North Pacific, Oreg. St. Univ. Press, Corvallis.
Ito, J. 1964. Food and feeding habits of Pacific salmon (Genus Oncorhynchus) in their ocean life. Bull. Hokkaido
Reg. Fish. Res. Lab. 29:85-97. (Fish. Res. Board Can. Transl. Ser. 1309).
Laval, P. 1980. Hyperiid amphipods as crustacean parasitoids associated with gelatinous zooplankton. Oceanogr.
Mar. Bio. Ann. Rev., 18:11-56.
LeBrasseur, R. j. 1966. Stomach contents of salmon and steelhead trout in the northeastern Pacific Ocean. Can.,
Fish. Res. Bd., )., 23:85-100.
Lorz (Van Arsdale), H., and W. G. Pearcy. 1975. Distribution of hyperiid amphipods off the Oregon coast. Can.,
Fish. Res. Bd., J., 32:1442-1447.
Merkel, T. ). 1957. Food habits of king salmon, Oncorhynchus tshawytscha (Walbaum), in the vicinity of San
Francisco, California. Calif. Fish. Game, 43(4):249-270.
Miller, D. R., J. G. Williams, and C. W. Sims. 1983. Distribution, abundance and growth of juvenile salmonids off
the coast of Oregon and Washington, summer 1980. Fish. Res. (Amsterdam) 2:1-17.
Oregon Department of Fish and Wildlife. 1982. Comprehensive plan for production and management of Oregon's
anadromous salmon and trout. Part 2. Coho salmon plan. Oreg. Dep. Fish Wildl., Fish Div., Anadromous Fish.
Sect., Portland, Oreg.
Peterson, W. T., R. D. Brodeur, and W. A. Pearcy. 1983. Feeding habits of juvenile salmonids in the Oregon coastal
zone in )une 1979. Fish Bull., U.S. 80(4): 841-851.
Pinkas, L., M. S. Oliphant, and I. L. K. Iverson. 1971. Food habits of albacore, bluefin tuna, and bonita in California
waters. Calif. Dept. Fish Game, Fish. Bull. (152):1-105.
Reimers, P. E. 1964. A modified method of analyzing stomach contents with notes on the food habits of coho
salmon in the coastal waters of Oregon and southern Washington. Fish. Comm. Oreg. Res. Briefs 3:32-40.
Richardson, S. L., and W. G. Pearcy. 1977. Coastal and oceanic fish larvae in an area of upwelling off Yaquina
Bay, Oregon. Fish. Bull., U.S. 75:125-145.
Silliman, R. P. 1941. Fluctuations in the diet of chinook and silver salmon (Oncorhynchus tshawytscha and O.
kisutch) of Washington as related to the troll catch of salmon. Copeia, 2:80-87.
Terry, C. 1976. Stomach analysis methodology: still lots of questions. Pages 87-92. in, C. A. Simenstad and S. J.
Lipovsky, (eds.), Fish Food Habits Studies, 1st Pacific Northwest Technical Workshop. Univ. Wash. Press,
Seattle.
Youngbluth, M. 1976. Vertical distribution and diel migration of euphausiids in the central region of the California
current. Fish. Bull., U.S. 74:925-936.
Zaret, T. M., and A. S. Rand. 1971. Competition in tropical stream fishes: support for the competitive exclusion
principle. Ecology, 52:336-342.
FALLOW AND BLACK-TAILED DEER CENSUS 47
Calif. Fish and Came 72(1): 47-61 1 986
LINE-TRANSECT CENSUSES OF FALLOW AND BLACK-
TAILED DEER ON THE POINT REYES PENINSULA i
PETER j. P. COCAN
Department of Forestry and Resource Management
University of California
Berkeley, California 94720
STEVEN C. THOMPSON 2
WILLIAM PIERCE 3
Point Reyes National Seashore
Point Reyes, California 94956
AND
REGINALD H. BARRETT
Department of Forestry and Resource Management
University of California
Berkeley, California 94720
Fallow and black-tailed deer are sympatric on Point Reyes Peninsula. Management
objectives of the National Park Service require accurate monitoring of trends in
numbers and composition of both species. Line transect sampling was coupled with
refined estimation techniques to calculate density of fallow deer in the coastal
prairie habitat type and for black-tailed deer in both coastal prairie and coastal scrub
habitat types and in a mosaic of both types. Density estimates are higher (fallow —
20.3/km 2: black-tailed — 9.4-20.7/km 2) than recorded by other census techniques.
Neither species was observed frequently enough in the forest type for analysis. The
sampling effort required to generate a population estimate with a coefficient of
variation of 20% or less is 43 km for both species in coastal prairie, and 83 km and
150 km for fallow and black-tailed deer, respectively, in coastal scrub, and 42 km for
black-tailed deer in the mosaic.
INTRODUCTION
The introduction of pastoralism to the Point Reyes Peninsula in the 1830's
initiated a trend which has continued to this day. The species composition and
abundance of large herbivores was transformed rapidly from one of tule elk,
Cervus elaphus, and black-tailed deer, Odocoileus hemionus, to include cattle,
Bos taurus, horses, Equus caballus, pigs, Sus scrofa, goats, Capra spp., and sheep,
Ovis aries (Toogood 1980). This stabilized in the latter part of the 19th century
with extirpation of the tule elk (Mason 1970), elimination of pigs and range
horses, and establishment of productive dairies (Toogood 1980). The indige-
nous human population died off or was resettled (Toogood 1980). Land was
cleared of brush to increase pastorage and for silage production, and a wide
range of exotic plants was introduced (Heady et al. 1977). Grizzly bear, Ursus
arctos, were extirpated sometime after the 1860's (Van Atta 1946), and moun-
tain lion, Felis concolor, were possibly absent from the early 1930's through the
early 1970's. Numbers of golden eagles, Aquila chrysaetos, and bald eagles,
Haliaeetus leucocephalus, were greatly reduced. Coyote, Canis latrans, were
eliminated in the 1940's (Clark 1982), but have been sighted sporadically since
1982. A population of red foxes, Vulpes vulpes, has become established in the
' Accepted tor publication May 1985. This is Welder Wildlite Foundation Contribution Number 155.
2 Mr. Thompson's present address: Division of Wildlite and Fisheries Biology, University of California, Davis,
California 95616.
1 Mr. Pierce s present address: Shenandoah National Park, Luray, Virginia 22835.
48 CALIFORNIA FISH AND CAME
vicinity of the Point Reyes Headlands as the result of an unauthorized introduc-
tion. In the 1940's, populations of axis deer, Axis axis, and fallow deer, Dama
dama, were established (Wehausen and Elliott 1982). Tule elk were reintro-
duced in 1978. Sympatric use of rangelands by wild and domestic ungulates has
led to the establishment of livestock diseases in the wild ungulate populations
(Rafiquzzaman 1977, Riemann et al. 1977, Jessup et al. 1981).
Little is known of the impact of these activities on numbers and distribution
of the resident population of black-tailed deer. Generally, California's deer popu-
lations were reduced markedly between 1849 and 1900 (Longhurst, Leopold,
and Dasmann 1952). However, numbers of native deer in California's north-
coastal counties have been declining since 1969 (Longhurst et al. 1976). The
magnitude of any shift in numbers of black-tailed deer on the Point Reyes
Peninsula is unknown.
With the establishment of Point Reyes National Seashore in the 1960's, pastor-
alism was halted over much of the peninsula. However, the Seashore's natural
resource management plan (National Park Service 1976) delineates a pastoral
zone in which traditional livestock production is to be permitted to continue. The
plan also calls for limiting numbers of exotic deer to no more than 350 of each
species while maintaining a healthy population of black-tailed deer. A direct
reduction program undertaken by Seashore staff in the pastoral zone removed
several hundred exotic deer between 1976 and 1981. Axis deer remain confined
to the pastoral zone and total approximately 250 (Thompson, unpubl. data).
Fallow deer were estimated to number 523 in 1977 (Wehausen and Elliott 1982).
Frequent observations of fallow deer suggest that their numbers have continued
to increase. The population is widespread over much of the peninsula. Conse-
quently, the exotic deer reduction program was extended into the southern zone
in 1980.
The management mandate requires manipulation of exotic deer populations
coupled with an ability to monitor trends in numbers and distribution of all deer
species. The Seashore's deer populations have been censused sporadically by
aerial total counts (Wehausen and Elliott 1982) and sample area counts (Das-
mann and Taber 1955, Elliott, unpubl. data, Nystrome and Stone, unpubl. data,
Thompson, unpubl. data), and by drive counts (Elliott, Wehausen, and Barrett,
unpubl. data). However, each method has serious disadvantages. The tendency
to underestimate population size by total counts is well documented (Norton-
Griffiths 1978), as is the potential of observers in aerial counts to underestimate
group size or overlook groups (Graham and Bell 1969, Pennycuick and Western
1972, Caughley 1974). Sample area counts require a novice observer to spend
at least 4 months becoming familiar with the area's topography and the distribu-
tion and habits of the target species (Elliott, unpubl. data).
As an alternative, we elected to explore the feasibility of making annual
population estimates of deer numbers on the Point Reyes Peninsula using line-
transect censuses. Specific objectives of the southern zone censuses were to: ( i )
estimate fallow deer densities, age and sex composition, and color phase, (ii)
evaluate changes in the above relative to the reduction program, (iii) estimate
black-tailed deer densities, age and sex composition, and (iv) detect any disper-
sal of axis deer into the area.
The objective of the pastoral zone census was to estimate black-tailed deer
densities, age, and sex composition.
FALLOW AND BLACK-TAILED DEER CENSUS
49
Results from censuses in both areas were used to calculate the sampling
intensity required to obtain a population estimate with a coefficient of variation
of 20% or less.
STUDY AREA
The Point Reyes Peninsula lies about 32 km northwest of San Francisco,
California, immediately west of the San Andreas fault zone ( Figure 1 ) . Inverness
Ridge forms a backbone along the peninsula, rising to a height of 448 m at Mount
Wittenburg and dropping abruptly into the sea at Tomales Point. A broad, flat
arm protrudes into the Pacific Ocean.
^\^ Sonoma County
Contra Costa County
int Reyes Station
pt Re'yeTTIeaaianb-s- —
FIGURE 1. Location of the pastoral and southern zones in Point Reyes National Seashore.
50 CALIFORNIA FISH AND CAME
The study area embraces two units of Point Reyes National Seashore: a
southern zone of 11,150 ha, chiefly designated wilderness, and a pastoral zone
of 8,100 ha. Ranching activities were halted in all but a few peripheral portions
of the southern zone and most domestic stock were removed between 1 962 and
1972. A network of former ranch roads are used as hiking trails by large numbers
of visitors. Traditional livestock practices continue in the pastoral zone, including
both beef and dairy ranches. Annual stocking rates average 0.33 animal units/ha
(Elliott 1982).
The vegetation has been mapped in detail (Lauer 1972) and may be catego-
rized into three general types (Figure 2): (i) forest, (ii) coastal scrub, and (iii)
coastal prairie (Kuchler 1977). The forest consists of extensive stands of Dou-
glas-fir, Pseudotsuga menziesii, and California laurel, Umbellularia califomica,
with riparian woodlands of alders, Alnus spp., and willows, Salix spp. Stands of
Bishop pine, Pinus muricata, occur along the eastern boundary. Coastal shrub
dominated by coyote bush, Baccharis pilularis, is common on north-facing
slopes. Species composition is more diverse and includes sagebrush, Artemisia
califomica, and poison oak, Rhus diversiloba (Grams et al. 1977) . Coastal prairie
is dominated by California brome, Bromus carinatus, tufted hairgrass, De-
schampsia caespitosa and sheep sorrel, Rumex acetosella, although fallow fields
support an abundance of annuals (Elliott and Wehausen 1974). In the southern
zone, forest is the most extensive habitat type, especially abundant in the south-
eastern portion of the area (5,018 ha or 45% of the total area) (Figure 2).
Coastal scrub lies as a belt intermediate between forest and prairie (3,456 ha;
31%). Prairie is prevalent in the northwest section and occurs elsewhere as a
narrow band along the coastline and eastern boundary (2,676 ha; 24%). In the
pastoral zone many scrub fields have been cleared to favor pastorage produc-
tion. Both prairie and scrub have been tilled and planted to a combination of
oats, Avena saliva, and vetch, Vicia spp., for silage production (Elliott 1982).
METHODS
Transects were run by Seashore personnel; the resulting data were analyzed
with program TRANSECT (Burnham, Anderson, and Laake 1980) on an IBM
4341 A computer at the University of California, Berkeley. Three censuses were
made of fallow and black-tailed deer in the southern zone in 1980, 1981, and
1982. Black-tailed deer were censused in the pastoral zone once in 1980. Sam-
pling methods differed only slightly between the southern and pastoral zones.
Transect lines were located differently in the two areas, and fallow deer were
recorded only in the southern zone. Identical procedures were used to estimate
density and calculate required future sampling efforts.
Location of Transects
In the southern zone, the distribution of the three habitat types was plotted
on USGS 7.5-minute quadrangle maps and their area determined by applying a
dot-grid transparency (Avery 1975). The trail system was broken into numbered
1-km sections. Twenty numbered trail sections were selected at random within
each habitat type. The ends of selected sections were located in the field and
marked with 1-m pieces of rebar. Transects were walked by two-person teams
from 16 to 20 September 1980, 21 to 24 September 1981, and 25-28 November
FALLOW AND BLACK-TAILED DEER CENSUS
51
1982. Team movements were coordinated to ensure that deer along transects
were not disturbed prior to being censused. Counts were made within 3 hours
of sunrise.
In the pastoral zone, a universal transverse mercator (UTM) grid 500 m on
each side was applied to a 7.5-minute USGS map. Points along the main road
system intersected by the grid were numbered and 30 points were selected at
random. At each point, a direction of true east or true west was randomly
selected. A line 1-km in length was laid out in the selected direction. We
determined whether the transect traversed any obstacles (ravines, scrub fields)
judged to be impassable on foot by use of a combination of aerial photographs,
the USGS map, and on-site inspection. If so, the alternate direction was evaluat-
ed under the same criteria. If both directions were considered impassable, the
point was discarded and another selected at random. This process was repeated
until 30 1-km transects either east or west had been selected. The points were
marked at the roadside with a 1.3-m length of rebar. Transects were traversed
on foot by two-person teams within 3 hours of sunrise between 8 and 12
December 1980. Each team maintained its direction by compass and determined
the distance traveled by pedometer and reference to aerial photographs.
PASTORAL
FIGURE 2. Distribution of vegetative types in the southern zone of Point Reyes National Seashore.
52 CALIFORNIA FISH AND GAME
Data Recorded
Upon sighting deer, observers recorded species, group size, sighting angle
measured with a compass, and sighting distance to the center of each group,
measured with an optical range finder. Group composition was recorded as
adult (1 + years), male or female and unsexed fawns for both deer species.
Color phases of fallow deer were recorded as: (i) white, (ii) black, and (iii)
other. The latter category consisted of both "common" and "menil" animals
(Chapman and Chapman 1982), not readily distinguished in the field.
Data Analyses
Each group is treated as a single sighting. Estimates of density of deer groups
were calculated from appropriate data sets with the Fourier series, exponential
polynomial, and exponential power series estimators of program TRANSECT
(Burnham et al. 1980). Each estimator uses a different model to describe the
probability density function (PDF). The Fourier series is recommended as a
general estimator as it is nonparametric and both, "model robust, pooling robust,
and has the shape criterion and high estimator efficiency" (Burnham et al.
1980:133). However, the Fourier series seriously underestimates density if ani-
mals move away from the observer prior to detection. The extent to which deer
move away from the transect line prior to detection cannot be measured.
However, a frequency distribution of observation distances with fewer observa-
tions in the grouping interval closer to the observer is indicative of deer move-
ment away from the observer prior to detection. The exponential power series
and exponential polynomial estimators are more robust than the Fourier series
to this possibility. A chi-squared test of the distribution of observations relative
to each model's PDF provides the criteria to select the most appropriate model.
A sample size of at least 40 observations is recommended (Burnham etal. 1980).
Only our sample for the pastoral zone transects exceeds this minimum. Howev-
er, we analyzed all samples of 30 or more observations. Samples of between 30
and 40 observations may be expected to generate numerically reliable estimates
of population density but with increased variances (Burnham, pers. commun.).
All observations of deer in the southern zone over 300 m from the line of travel
were omitted. The remainder were grouped into perpendicular distance classes
of 0-30, 31-60, 61-90, 91-120, 121-180, 181-240, and 241-300 m prior to
analysis by program TRANSECT (Burnham et al. 1980). Selection of a width of
300 m complies with the recommendation of Burnham et al. (1980) of removing
the effect of outlier observations while maintaining a transect width considerably
larger than the mean perpendicular sighting distance. Observations of deer
groups in the pastoral zone were truncated at a perpendicular distance of 250
m and grouped into 30-m intervals to 120 m, 121 to 180 m, and 181 to 250 m
for analysis by program TRANSECT (Burnham et al. 1980). A width of 250 m
ensured no overlap between adjacent transect lines. Grouping helps remove the
effect of rounding errors and observer variation in measuring sighting distance
and angle (Burnham, Anderson, and Laake 1981).
The density of individuals was calculated by combining an estimate of group
density and its standard error with the mean and standard error of group size
(Burnham et al. 1981:475). The standard error is used to calculate a 90%
confidence interval of the estimate. Numbers were obtained by multiplying the
density estimate by the area calculated for each habitat type in the southern
FALLOW AND BLACK-TAILED DEER CENSUS 53
zone or by the area of the pastoral zone.
The length of transect line required for a desired percent coefficient of varia-
tion based upon the variability of a pilot survey is calculated by the formula:
b L,
L =
(CV2(D))2 n
( Burnham et al. 1 980:36) where L is the length of transect line required to obtain
a desired coefficient of variation (CV2(D)) and n, is the number of animal
groups sighted in a pilot census of length L,. The factor b is calculated from the
formula:
b = n, (CV,(D))2
where n, is as above and (CV,(D) ) is the coefficient of variation of the pilot
survey. A value of b = 3 is recommended as slightly overestimating the sample
required (Burnham et al. 1980:35) and is used in our calculations.
Estimates were made of the length of transect line required for a coefficient
of variation of 20 percent using the 1980 counts for the southern zone and the
single count for the pastoral zone as pilot surveys.
RESULTS AND DISCUSSION
Population Composition
Southern Zone
Fallow and black-tailed deer were sighted in all habitat types (Table 1 ). No
axis deer were seen in the southern zone in any year. Thirty or more groups of
fallow deer were sighted only once in any habitat type. Thirty or more groups
of black-tailed deer were sighted in grassland in all years and in scrub in 1981.
The paucity of observations of both species in the forest type should not be
interpreted as indicative of low densities, as the number of animals sighted is a
poor index to density (Burnham et al. 1981 ). Rather, it simply reflects a failure
to sight adequate numbers for analysis at our sampling intensity.
The number of groups of fallow deer sighted declined continuously over the
3 years (Table 1 ). This is undoubtedly due in part to the removal of animals but
likely is attributable also to a general shift in the distribution of fallow deer away
from trails and out of the area in response to shooting pressure. Rangers ob-
served a concurrent increase in the abundance of fallow deer in the pastoral
lands to the north. Movement of fallow deer in response to shooting has been
reported elsewhere (Chapman and Chapman 1982). Similarly, Houston (1982)
noted that elk avoided areas adjacent to roads for a number of years following
a reduction program. A Kruskall-Wallis test of differences in mean group sizes
between habitat types for all years was highly significant (X2, P < .001).
Average group size was consistently largest in the prairie type. Schall (1982)
reported similar findings in Alsace Province, France.
A contingency test shows the proportions of age and sex classes of fallow deer
for all years (Table 2) are significantly different (X2, P < .01 ). The ratio of males
and fawns to female fallow deer was notably higher in 1980 and 1981 than in
1982. Partitioning the contingency table (Zar 1974) revealed a non-significant
difference between 1980 and 1981 (X 2, P < .10). The difference between the
first two and third years likely reflects a difference in the visibility of males in
September 1980 and 1981 in contrast to November 1982, and a low proportion
of fawns in 1982.
54
CALIFORNIA FISH AND CAME
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56 CALIFORNIA FISH AND GAME
The age ratios reported in this study are consistently lower than observed in
the 1970's (Wehausen 1973, Wehausen and Elliott 1982).
The white color phase was predominant in the original introduction (Wehaus-
en 1973) and remains prevalent in adults. Few fawns are classified as white
because the white phase is a light tan color through the first year of life (Wehaus-
en 1 973 ) . The possibility of adult color or group size influencing detectability of
fallow deer measured by perpendicular sighting distance was investigated by
subjecting the 1980 observations to a 3-way analysis of variance (Sokal and
Rohlf 1969) on the effect of: (i) habitat type, (ii) group size classified as one
or greater than one, and (iii) animal color classified as white or nonwhite. A
significant (P — 0.10) difference in observability was found only between habi-
tat types. Thus, the proportions of color phases may be considered representa-
tive.
No trend was evident in the number of black-tailed deer groups observed
during the three counts (Table 1 ), indicating no tendency for this species to
move away from trails in response to shooting. The higher number of observa-
tions in 1981 reflects an increase in sightings in scrub for one year. A Kruskall-
Wallis test of differences in mean group sizes between habitat types was non-
significant (X2, P < .14). A contingency test shows differences in proportions
of age and sex classes between years (Table 3) are highly significant (X2, P <
.0005). The ratio of males and fawns to female black-tailed deer was notably
higher in 1980 and 1981 than in 1982. Partitioning the contingency (Zar 1974)
revealed a non-significant difference between 1980 and 1981 (X2, P < .25).
TABLE 3. Sex and Age Composition of Black-tailed Deer in the Southern Zone of Point
Reyes National Seashore in 1980, 1981, and 1982. Percent given in parentheses.
Year
1980
1981
1982
Total
Sex and
age class
Males:
deer
Males
Females
Fawns
Unknowns
100 Females: Fawns
100
40 (40)
42 (42)
14 (14)
4 (4)
95:
100 : 33
120
56 (47)
46 (38)
16 (13)
2 (2)
122:
100 : 35
90
20 (22)
61 (68)
9 (10)
0
33:
100 : 15
The above differences likely reflect differences in the timing of the 1980 and
1981 censuses, as opposed to 1982. The marked decline in the number of adult
males: 100 females in 1982 may be attributable to differences in the behavior of
males at the close of the rut in late November (Dasmann and Taber 1956). Adult
males are likely over-represented in herd composition counts made during the
rut from late September through November (Dasmann and Taber 1956, Taber
and Dasmann 1958).
Pastoral Zone
A total of 195 black-tailed deer in 54 groups was sighted along the 30 km of
transect in the pastoral zone. Group size ranged from solitary individuals to 12.
The ratio of males to females (Table 4) approximates ratios recorded in the
southern zone in November 1982 (Table 3) and the pastoral zone in October
1971 (Elliott, Wehausen and Barrett, unpubl. data). The ratio of 32 fawns: 100
females is similar to our observations in the southern zone in November 1980
and 1981 (Table 3). A ratio of 64 fawns: 100 does was recorded in January and
February 1981 over a smaller portion of the pastoral zone (Thompson, unpub.
data). Composition counts made in the north coast range of California in mid-
December are likely to be representative of the population ( Dasmann and Taber
1956, Taber and Dasmann 1958).
FALLOW AND BLACK-TAILED DEER CENSUS 57
TABLE 4. Sex and Age Composition of Black-tailed Deer in the Pastoral Zone (n = 195) of
Point Reyes National Seashore in 1980. Percent given in parentheses.
5ex and age class
Males: Females: Fawns Males: 100 Females: Fawns
30 (15) 125 (64) 40 (21) 24 : 100 : 32
Density Estimates
Southern Zone
Insufficient observations were made of fallow deer in either the coastal scrub
or forest habitats in 1980 to calculate densities. Counts in 1981 and 1982 were
made in areas likely being avoided by fallow deer and are not suitable for
analysis. Thus, fallow deer density is calculated only for the coastal prairie
habitat type in 1980. Observations of black-tailed deer in the coastal prairie type
were judged to be adequate to generate annual estimates of density in each year
together with an averaged and pooled estimate for all 3 years combined (Burn-
ham et al. 1981). Observations in the coastal scrub type were sufficient to
generate an estimate of density only in 1980.
The population estimate for fallow deer (Table 5) superficially approximated
results of a minimum total count of 523 from a helicopter survey centered on
the pastoral lands in 1977 (Elliott, unpubl. data, Wehausen and Elliott 1982).
However, density estimates derived from previous counts ranged between 0.08
(Wehausen 1973) and 0.07 (Elliott, unpubl. data) deer/ ha in contrast to the
estimate of 0.20 deer/ ha from this study. The lower limit of the 90% confidence
interval approximated these earlier estimates, as did an estimate derived by
simply using the total number of fallow deer sighted in prairie in 1980. We
suggest that these differences resulted more from different methods of sampling
and data analysis than from real shifts in population density. Densities of three
fallow deer populations in England ranged from 0.38 to 6.00 animals/ha (Bailey
and Putman 1981).
TABLE 5. Fourier Series Estimate of Fallow Deer Density (N/ha) and Numbers in the
Coastal Prairie Habitat Type, Southern Zone, Point Reyes National Seashore, in
1980.
Deer groups/ha Deer/ha Population 90% Confidence
Density 5. F. Density S. F. estimate interval
0.0549 0.0189 0.203 0.075 543 205-881
The three annual estimates of black-tailed deer density in the prairie section
of the southern zone showed remarkable consistency among years (Table 6).
Although the estimate of deer group density was greatest in 1981, the estimate
of population density was not as high, because mean group size was relatively
small that year (Table 1 ). Considerable reduction of the standard error of the
density estimate was achieved by averaging or pooling the three separate esti-
mates. The ability to average or pool samples gathered over time permits in-
creased precision in density estimates as monitoring continues. More precise
estimates may detect long-term shifts in population densities obscured by high
variance in individual samples.
58 CALIFORNIA FISH AND CAME
TABLE 6. Annual, Weighted Averaged and Pooled Fourier Series Estimates of Black-tailed
Deer Density (N/ha) and Numbers in the Coastal Prairie Habitat Type, Southern
Zone, Point Reyes National Seashore, in 1980, 1981 and 1982.
90%
Deer groups/ha Deer/ha Population Confidence
Year Density S. E. Density S. E. estimate interval
1980 0.0626 0.01125 0.127 0.0260 340 249-431
1981 0.0798 0.01598 0.138 0.0380 370 237-503
1982 0.0691 0.01545 0.142 0.0346 380 259-501
Weighted Averaged 0.0753 0.00501 0.145 0.0126 388 344-^32
Pooled 0.0744 0.00504 0.144 0.0126 385 341^129
Selection of the exponential polynomial estimator in the coastal scrub type
(Table 7) suggests movement of black-tailed deer away from the observers prior
to detection. It may reflect greater difficulty in detecting black-tailed deer in the
denser vegetation.
TABLE 7. Exponential Polynomial Estimate of Density (N/ha) and Population Size of Black-
tailed Deer in Coastal Scrub, Southern Zone, Point Reyes National Seashore, 1981.
Deer groups /ha
Deer/ha
Population
estimate
324
90% Confidence
Density S. E.
0.0612 0.0207
Density S. E.
0.094 0.033
interval
127-521
Sample area counts (Taber and Dasmann 1955) of black-tailed deer on select
sites within the Seashore's southern zone yielded density estimates of 0.06-0.17
deer/ha (Elliott 1982).
The length of transect line required to obtain future estimates of fallow and
black-tailed deer densities with a confidence interval of 20% in coastal prairie
are identical (Table 8). A comparable estimate for fallow deer in coastal scrub
habitat type requires approximately twice the sampling effort while a compara-
ble estimate for black-tailed deer in coastal scrub requires approximately four
times the sampling intensity. This is not to imply that a specific number of
transects need be established. Fewer transects may be permanently marked and
sampled an appropriate number of times.
TABLE 8. Calculated Length (km) of Transect Line Required to Obtain Estimates of Popula-
tion Density with a Coefficient of Variation of 20 percent or Less for Fallow and
Black-tailed Deer by Habitat Types.
Deer species
Habitat type Fallow Black- tailed
Coastal prairie 43 43
Coastal scrub 83 150
Mosaic - 42
TABLE 9. Fourier Series Estimate of Density (N/ha) and Population Size of Black-tailed
Deer in the Pastoral Zone, Point Reyes National Seashore, 1980.
Deer groups/ha Deer/ha Population 90% Confidence
Density S.E. Density S.E. estimate interval
0.0583 0.0143 0.2069 0.0555 1790 826-2753
The exponential power series provided the best fit to the data, suggesting
some movement of deer away from the transect line prior to detection by the
census team. The estimate of black-tailed deer density (Table 9) in the pastoral
FALLOW AND BLACK-TAILED DEER CENSUS 59
zone is higher than those derived for the southern zone. Similarly, this density
estimate is higher than estimates of black-tailed deer density in a select portion
of the pastoral zone obtained by drive counts (Elliott, Wehausen and Barrett,
unpubl. data) or sample area counts (Elliott 1982:131). Thompson (unpubl.
data) found that the widely scattered distribution of black-tailed deer made
sample area counts difficult.
CONCLUSIONS
The results demonstrate the value of line transect censuses and analysis by
program TRANSECT in estimating population density and monitoring long term
shifts in density.
Estimates of density and age and sex structure of fallow and black-tailed deer
generated from line transect sampling on portions of the Point Reyes Peninsula
suggest higher densities of both species than previously recorded. We attribute
these higher estimates to differences in sampling procedures and data analysis
rather than true shifts in population density. In particular, modeling of perpen-
dicular detection functions by program TRANSECT provides a more realistic
assessment of the abundance of target species. Such an assessment is a step in
countering the almost universal tendency to underestimate population densities.
We recognize both sets of line transects rely heavily on the location of existing
roads and trails in their design. Such counts may be biased, as roads may be
constructed through habitats selected or avoided by the species in question
(Norton-Griffiths 1978). Proposed modifications of census procedures present-
ed under recommendations provide an opportunity to reduce the difficulties
encountered in this preliminary study.
RECOMMENDATIONS
The recommended procedure for estimating numbers of fallow and black-
tailed deer on the Point Reyes Peninsula is as follows:
(i) Census both species throughout their total known range on the Point
Reyes Peninsula to reduce the possibility of shifts in distribution affecting census
results.
( ii ) Distribute permanently marked transect lines randomly and independent-
ly within prairie and scrub habitat types over the total area. Transects should be
located independently of roads and major trails to the extent feasible. Sampling
intensity should be at the level calculated from our pilot surveys.
( iii ) Establish an index of abundance for each species in all habitat types and
determine the linearity of the relationship. Comparison of the index between
habitat types with density estimates to those with no density estimates may
provide an approximation of density in the latter.
(iv) Evaluate the potential of obtaining population estimates from change-in-
ratio estimators (Hanson 1963, Paulik and Robson 1969). Values of interest
include the ratio of fallow to black-tailed deer and the ratio of age classes, sexes
or color phases of fallow deer prior to and subsequent to the annual reduction
program. Records must be kept on the age, sex, and color phase of shot deer.
Estimates could be derived from observations made while walking the line
transects discussed above. Bias may occur if a certain age or sex class of the
population becomes more wary than others or if fallow deer become more
secretive than black-tailed deer.
60 CALIFORNIA FISH AND CAME
(v) Count fallow deer from a helicopter or fixed-wing aircraft. Results of
aerial counts could be compared to concurrent line transect ground counts.
Aerial counts should be done along permanent transects from an aircraft fitted
with sophisticated navigation equipment and radar altimeter to ensure the data
acquired benefit from analysis by program TRANSECT. We do not suggest a
double sampling design using line transects. The greatest advantage of an aerial
census is the complete independence of location of transects from roads and
trails, or topographic and vegetative features likely to influence locating ground
transects. It is unlikely that black-tailed deer will be consistently detectable from
an aircraft.
ACKNOWLEDGMENTS
This report represents the combined efforts of a great number of people. K.
Rogers and P. Sugnet surveyed trails, delineated habitat boundaries and selected
transect locations in the south. A. Soost and J. Hartley re-marked transects in
1 981 . Seashore staff and volunteers covered many kilometers of trails conducting
the censuses. M. Raphael assisted with analyses involving program TRANSECT.
J. Verner and B. Noon offered constructive review of the manuscript. The senior
author was supported by a fellowship from the Rob and Bessie Welder Wildlife
Foundation during portions of this study. Additional support was provided by
Project 3501 -MS of the California Agricultural Experiment Station.
LITERATURE CITED
Avery, T. E. 1975. Natural resource measurements. 2nd ed. McGraw-Hill Book Co., New York, NY. 339 p.
Bailey, R. E., and R. ). Putman. 1981. Estimation of fallow deer populations from faecal accumulation. J. Appl. Ecol.,
18(4) : 697-702.
Burnham, K. P., D. R. Anderson, and). L. Laake. 1980. Estimation of density from line transect sampling of biological
populations. Wildl. Monogr., 72 : 1-202.
1 981 . Line transect estimation of bird population density using a Fourier series. Studies in Avian Biology,
6 : 466-482.
Caughley, C. 1974. Bias in aerial survey, j. Wildl. Manage., 38(4) : 921-933.
Chapman, N. C, and D. I. Chapman. 1982. The fallow deer. Forest Record 124. Her Majesty's Stationary Office.
19 p.
Clark, K. E. 1982. The mammals of the Point Reyes Peninsula. Unpubl. Thesis, Univ. of California, Santa Cruz. 149
P-
Dasmann, R. F., and R. D. Taber. 1955. A comparison of four deer census methods. Calif. Fish Came, 41 (3) :
225-228.
1956. Determining structure in Columbian black-tailed deer populations. ). Wildl. Manage., 20(1) :
78-83.
Elliott III, H. W. 1982. A study to assess competition and carrying capacity among the ungulates of Point Reyes
National Seashore. Dissertation, Univ. of California, Davis. 197 p.
, and ). D. Wehausen. 1974. Vegetational succession on coastal rangeland of Point Reyes Peninsula.
Madrono, 22(5) : 231-238.
Graham, A., and R. Bell. 1969. Factors influencing the countability of animals. E. Afr. Agric. For. J., 34 (special issue)
: 38-43.
Grams, H. )., K. R. McPherson, V. V. King, S. A. MacLeod, and M. G. Barbour. 1977. Northern coastal scrub on
Point Reyes Peninsula, California. Madrono, 24(1) : 18-24.
Hanson, W. R. 1963. Calculation of productivity, survival, and abundance of selected vertebrates from sex and
age ratios. Wildl. Monogr., 9 : 1-60.
Heady, H. F„ T. C. Foin, M. K. Hektner, D. W. Taylor, M. G. Barbour and W. ). Barry. 1977. Coastal prairie and
northern coastal scrub. Pages 733-757 in M. G. Barbour and ). Major, eds. Terrestrial vegetation of California.
John Wiley and Sons, New York, NY. 1002 p.
Houston, D. B. 1982. The northern Yellowstone elk. MacMillan Publishing Co., Inc., New York, NY. 474 p.
Jessup, D. A., B. A. Abbas, D. Behymer, and P. Gogan. 1981. Paratuberculosis in tule elk in California. J. Am. Vet.
Med. Assoc, 179(11 ):1252-1254.
FALLOW AND BLACK-TAILED DEER CENSUS 61
Kuchler, A. W. 1977. The map of the natural vegetation of California. Pages 909-938 in M. C. Barbour and ). Major,
eds. Terrestrial vegetation of California. John Wiley and Sons, New York, NY. 1002 p.
Lauer, D. T. 1972. Vegetation mapping at Point Reyes National Seashore. Pages 86-95 in R. N. Colwell and G. A.
Thorley, eds., ERTS-1 data as an aid to resource management in northern California. Center for Remote Sensing
Research, Univ. of California, Berkeley. 120 p.
Longhurst, W. M., A. S. Leopold, and R. F. Dasmann. 1952. A survey of California deer herds, their ranges and
management problems. Calif. Dep. Fish and Game, Game Bull. (6) :1— 136.
, F. O. Carton, H. F. Heady, and G. E. Connolly. 1976. The California deer decline and possibilities for
restoration. Proc. West. Sec. The Wildl. Soc, 1976 : 74-103.
Mason, ). 1970. Point Reyes, The solemn land. North Shore Books. Inverness, CA. 198 p.
National Park Service. 1976. Natural resources management plan and environmental assessment: Point Reyes
National Seashore, California. Files of Point Reyes National Seashore. 159 p.
Norton-Griffiths, M. 1978. Counting animals. 2nd ed. African Wildlife Leadership Foundation, Nairobi, Kenya.
139 p.
Paulik, G. J., and D. S. Robson. 1969. Statistical calculations for change-in-ratio estimators of population parameters.
). Wildl. Manage., 33(1):1-27.
Pennycuick, C. J., and D. Western. 1972. An investigation of some sources of bias in aerial transect sampling of
large mammal populations. E. Afr. Wildl. )., 10(3):175-191.
Rafiquzzaman, M. 1977. Johne's disease (paratuberculosis) in cattle and exotic deer at Point Reyes, California.
Thesis, Univ. of California, Davis. 34 p.
Riemann, H. P., R. Ruppanner, P. Willeberg, C. E. Frnti, W. H. Elliott, R. A. Fisher, O. A. Brunetti, J. H. Aho, J. A.
Howarth, and D. E. Behymer. 1979. Serological profile of exotic deer at Point Reyes National Seashore. J. Am.
Vet. Med. Assoc, 175(9):911-913.
Schall, A. 1982. Influence de I'environment sur les composantes due groupe social chez le daim Cervus (Dama)
dama L. Revue Ecol., (Terre Vie) 36(2):161-174.
Sokal, R. R., and F. J. Rohlf. 1969. Biometry. W. H. Freeman and Co., San Francisco, CA. 776 p.
Toogood, A. C. 1980. Historic resource study. A civil history of Golden Gate National Recreation Area and Point
Reyes National Seashore, California. 2 vol. National Park Service, U.S. Dept. of the Interior. 376 p.
Taber, R. D., and R. F. Dasmann. 1958. The black-tailed deer of the Chapparal: its life history and management
in the North Coast Range of California. Calif. Dept. Fish and Game, Game Bull. (8):1-163.
Van Atta, C. E. 1946. Notes on the former presence of grizzly and black bears in Marin County, California. Calif.
Fish Game, 32(8):27-29.
Wehausen, J. D. 1973. Some aspects of the natural history and ecology of fallow deer on Point Reyes Peninsula.
Thesis, Univ. of California, Davis. 68 p.
, and H. W. Elliott III. 1982. Range relationships and demography of fallow and axis deer on Point Reyes
National Seashore. Calif. Fish Game, 68(3):132-145.
Zar, ). H. 1974. Biostatistical Analysis. Prentice-Hall, Inc., Englewood Cliffs, N). 620 p.
62 CALIFORNIA FISH AND GAME
Calif. Fish and Came 72(1): 62-64 1 986
NOTES
UTILIZATION BY SALT MARSH HARVEST MICE
REITHRODONTOMYS RAVIVENTRIS HALICOETES OF A
NON-PICKLEWEED MARSH
Management plans for private duck clubs in Suisun Marsh and a recovery plan
for the endangered salt marsh harvest mouse are being developed based upon
assumptions that those mice require pickleweed, Salicornia pacifica, dominated
habitats. The presence of pickleweed as the dominant plant species in the marsh
has been described for salt marsh harvest mice (Fisler 1965, Shellhammer 1977,
Shellhammer et al. 1982) and has been considered the necessary component of
optimal habitat ( Wondolleck, Zolan and Stevens 1976). Australian saltbush,
Atriplex semibaccata, fat hen, A. patula, gum plant, Crindelia cunifolia, and
cordgrass, Spartina foliosa, also regularly occur in lesser amounts in typical
optimal marsh habitat. The importance of a dense mat of cover and network of
open areas for salt marsh harvest mice has also been reported (Dixon 1909,
Hooper 1944, Wondolleck et al. 1976, Shellhammer 1977).
In May 1981, during rodent trapping surveys on the California Department of
Fish and Came Hill Slough Wildlife Area (eight kilometers southeast of Fairfield,
Solano County, California), eleven harvest mice were captured and released
during 300 trap nights of effort. The mice were identified as salt marsh harvest
mice using a combination of external measurements, color patterns and behav-
ior, assigned on a point system (Shellhammer 1984). The area appeared to
contain no pickleweed and consisted of ten hectares isolated on three sides by
large slough channels with a paved road on the fourth side. The area has been
diked off from brackish water inundation during high tides for approximately 50
years, although it retains some standing water for approximately four months
during the winter in years of high precipitation.
As a result of the discovery of salt marsh harvest mice on the area, a vegetation
transect of the ten hectare site was conducted. A representative cross-section
of the site was taken using the toe-point method. The vegetative transect re-
vealed the following: fat hen 45 percent, salt grass, Distichlis spicata, 14 percent,
annual grasses, 13 percent, baltic rush, Juncus balticus, 10 percent and alkali
heath, Frankinia grandiflora, 9 percent. Several other plant species occurred on
the site, including pickleweed, but each constituted less than one percent of the
total vegetative cover. Fat hen was quite dense and provided excellent cover for
the mice. This is the second report where salt marsh harvest mice were found
to inhabit an area not dominted by pickleweed and the first for the northern
subspecies. Rice (1974), found areas containing fat hen were actually preferred,
while areas containing pickleweed were avoided by the southern subspecies of
the salt marsh harvest mouse, R. r. raviventris. Zetterquist (1977) in her work
in the south San Francisco Bay concluded that her findings invalidated the idea
that R. r. raviventris occurs only in tidal salt marshes and that marginal areas
should be preserved in present condition or expanded.
This report is in accord with Rice's 1974 work and expands upon Shellham-
mer's 1982 findings. Further sampling and study are necessary to determine the
extent and intensity of use in such areas by salt marsh harvest mice. Additional
NOTES 63
findings may shed more light on the biology of the salt marsh harvest mouse and
have a bearing on management programs being developed to ensure the con-
tinued survival of this animal. Additional "marginal" areas should be examined.
No changes in current management practices affecting the salt marsh harvest
mouse are justified at this time. However, these findings indicate marginal areas
may be important to salt marsh harvest mice and such areas should not be
written off to development without investigation.
LITERATURE CITED
Dixon ). 1909. A new harvest mouse from Petaluma, California. Univ. Calif. Publ. Zool., 5 : 271-273.
Fisler, C.T. 1965. Adaptations and speciation in harvest mice of the marshes of San Francisco Bay. Univ. Calif. Publ.
Zool., 77: 1-108.
Hooper, E.T. 1944. San Francisco Bay as a factor influencing speciation in rodents. Misc. Publ., Mus. Zool., Univ.
Mich. 59: 1-89.
Rice, V.C. 1974. The population ecology of the salt marsh harvest mouse at Triangle Marsh. Thesis. San Jose State
Univ.
Shellhammer, H. 1977. Of mice and marshes. San )ose Studies., 3(1): 23-25.
1984. Identification of salt marsh harvest mice, Reithrodontomys raviventris, in the field and with cranial
characteristics. Calif. Fish Came, 70(2): 113-120.
, R. jackson, W. Davilla, A. Gilroy, H.T. Harvey and L. Simons. 1982. Habitat preferences of salt marsh
harvest mice (Reithrodontomys raviventris). Washmann ). Biol., 40(1-2): 102-114.
Wondolleck, ).T„ W. Zolan, and G.L Stevens. 1976. A population study of the harvest mouse (Reithrodontomys
raviventris Dixon) in the Palo Alto Baylands salt marsh. Wasmann ). Biol., 34(1): 52-64.
Zetterquist, D.K. 1977. The salt marsh harvest mouse (Reithrodontomys raviventris raviventris) in marginal habi-
tats. Wasmann ). Biol., 35(1): 68-76.
— Fred Botti, Dee Warenycia and Dennis Becker, California Department of Fish
and Game, Region III, P. O. Box 47, Yountville, California 94599. Accepted for
publication December 1984.
A METHOD FOR THE EFFICIENT REMOVAL OF JUVENILE
SALMONID OTOLITHS
During 1981 and 1982, juvenile steelhead rainbow trout, Salmo gairdneri
Richardson, were collected from three northern California watersheds for a
California Department of Fish and Game funded study on the racial analysis of
juvenile summer and winter steelhead and resident rainbow trout (Winter
1 983 ) . The fish were frozen for later removal and analysis of otoliths and otolith
nuclei as described by several authors (Kim 1963; McKern, Horton, and Koski
1 974; Rybock, Horton, and Fessler 1 975 ) . Three pairs of otoliths are found in the
inner ear of steelhead but only the largest pair, the sagittae, are used for age and
racial studies so use of the term "otolith" refers to the sagittae.
I soon discovered that the typical method of otolith removal, splitting the
head, was inadequate for thawed young-of-year steelhead since even razor
blades would mash the head before the blades would cut. McKern and Horton
(1970) described a punch that expedited removal of otoliths from larger steel-
head. However, a punch delicate enough for use on young-of-year fish was not
feasible. A method of otolith removal that did not result in mashed heads or the
loss of otoliths by having to probe for the granular otoliths was developed.
The otoliths were obtained from the fish by first removing the lower jaw and
all of the gill rakers to expose the neurocranium. For young-of-year fish, the
otoliths were visible through the semi-transparent walls of the neurocranium and
were easily removed by puncturing the walls with No. 5, fine-tipped forceps and
64
CALIFORNIA FISH AND GAME
pulling out the otoliths. For yearling and older fish, the neurocranium is opaque
and prevents visual location of the otoliths. In these cases, a probe was forced
through the neurocranium directly anterior to the area containing the otoliths
( Figure 1 ) . The fish were then grabbed between thumb and forefinger on either
side of the incision and bent backwards, thereby rupturing the neurocranial
cavity. The otoliths were then clearly visible in the posterior portion of the
neurocranium and were removed with fine-tipped forceps. The sacculus, the
membranous sac surrounding each sagitta, was removed by rubbing each otolith
between thumb and forefinger and the otoliths placed in water filled glass vials
for storage. This procedure was also used on several adult steelhead with success
but heavy scissors or wire cutters are recommended for cutting away the lower
jaw.
Right
Otolith
FIGURE 1.
Incision
Point
Left
Otolith
Ventral view of a young-of-year steelhead rainbow trout with lower jaw and gill rakers
removed, showing location of otoliths and neurocranium incision point.
LITERATURE CITED
Kim, W.S. 1963. On the use of otoliths of red salmon for age and racial studies. Thesis. Univ. of Washington,
Seattle, WA
McKern, |.L, and H.F. Horton. 1970. A punch to facilitate the removal of salmonid otoliths. Calif. Fish Came,
56(l):65-68.
McKern, J.L., H.F. Horton, and K.V. Koski. 1974. Development of steelhead trout (Salmo gairdneri) otoliths and
their use for age analysis and for separating summer from winter races and wild from hatchery stocks. Can.,
Fish. Res. Bd., )., 31:1420-1426.
Rybock, J.T., H.F. Horton, and ).L. Fessler. 1975. Use of otoliths to separate juvenile steelhead trout from juvenile
rainbow trout. Fish. Bull., 73(31:654-659.
Winter, B.D. 1983. Racial analysis of juvenile summer and winter steelhead and resident rainbow trout [Salmo
gairdneri Richardson) from three northern California watersheds. Thesis. Humboldt State Univ., Areata, CA.
— Brian D. Winter, Fisheries Resource Management, Nez Perce Tribe, P.O. Box
365, La^wai, ID 83540. The work reported was done as part of a Master's
thesis at Humboldt State University. Accepted for publication March 1985.
Photoelectronic composition by
• \\ II HUSH IHTM I 111 m mi niivriM.
so— NOTfvS
KIHXXIT
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